Mercedes-Benz S450 vs BMW XM

What's the difference?

Mercedes-Benz set out to restore the S-Class' place amongst the greatest sedans in the world.

In the heavily-optioned, near-$250K-plus S450 as well as the extended S450L at $300K as tested (the sweet spot of the range for now), we reckon the Germans have succeeded, pushing safety, comfort and technology boundaries, in a package that is true to the heritage of the series.

Tax-fuelled sky-high prices will certainly keep the S-Class niche in Australia, but the car is more than good enough to dominate its tiny corner of the upper-large luxury car sphere.

The best new car in the world? We reckon it's highly likely. Mission accomplished, Mercedes.

It’s pretty obvious the XM is designed to impress people with big wallets and an appetite for a techy experience that’s also not without a few green credentials. The ability to motor around as a fully-electric vehicle for up to 80km or so is a big plus and the electric-ballroom interior vibe is hard to ignore, as well.

But from our perspective, the full-fat, twin-turbo V8, while offering startling performance, is perhaps a lost opportunity to follow some of BMW’s competitors into the engine-downsizing space. Then again, when you floor the throttle and 2700kg hurtles forward like a big dog on a short chain, you can see where BMW is coming from.

Perhaps the biggest letdown is the ride quality – or lack of it. While it’s understandable BMW wanted the most dynamic version of the XM it could manage, the end result plays against the vehicle’s otherwise long suit of hyper-luxury. Doubtless, BMW would argue that to soften the chassis would have been to introduce a chink into a no-compromise product. But, perhaps, sometimes a sensible compromise is the way forward.

Most Mercedes models have followed the Russian Doll-style cookie-cutter styling theme, and the heavy family look continues with the W223.

Still, the flush door handles do add a touch of Tesla-esque modernity, while the elegant silhouette and clean lines are in keeping with the luxury aspirations. Larger in every dimension compared to the old W222, the S450 is some 71mm-longer in wheelbase (3106mm) than before while the LWB's has stretched out by 51mm (3216mm), benefiting proportions as well as interior packaging.

AMG-branded wheels look sporty but – in the S450 at least – they're perhaps a tad too gangster. A set of flush alloys would give it a more-modern and techier appearance, in our opinion.

Overall, however, the S-Class ‘7' possesses the prerequisite richness of design. It isn't as bold and mould-breaking as models like the W116 were back in their day, but the styling is still a success.

By the way, the latest S-Class is the first Mercedes to employ the MRA2 longitudinal platform, which is rich in lightweight steels (50 per cent aluminium), is correspondingly stronger than before but also 60kg lighter.

With a drag co-efficiency rating as low as 0.22Cd on some overseas grades, the W223 is one of the most aerodynamic production vehicles in history.

There’s nothing subtle about the way the XM looks. It probably pulls up just short of brutalist (or maybe not) but even those who find its slabs and angles attractive have to admit that it’s bold.

The now-trademark giant nostrils set the mood and the rest of the exterior suggests some kind of armoured transport for presidents rather than wheels for the school run. Doubtless, this will hardly be seen as a fault by those in the market for such a thing.

The real surprise here is that the XM does not share a bodyshell with any other production BMW. Sure, the V8 petrol engine and wheelbase are common to other BMW and M models, but the sheet metal is the XM’s and the XM’s alone. That in itself, is quite a statement of intent.

For the beginning of our day with the S-Class, we were chauffeured from home to a mansion in Kew, a blue-chip Melbourne suburb. Our heavily-optioned S450L featured most of the aforementioned extras – including the Business Class Package and Rear Entertainment Package – and the experience was predictably, sumptuously memorable.

Reclining individual rear seats with easy-reach tablets, armrests offering access to all multimedia and available climatised and massaging cushions and backrests... we're no longer in our normal ride, Toto.

Yet, all these trinkets and gizmos are mere add-ons, that can turn a stretched Caprice into a flash hen's night carriage if enough money and glitz is thrown at it.

No, the new S-Class must impress in an altogether less tangible and more philosophical manner, involving all the senses, and not just what we see, hear and touch. It must appeal beyond the superficial. Otherwise, it is not a large Mercedes-Benz luxury sedan in the classic manner.

This is a Herculean task for the Stuttgart designers and engineers. By and large, though, the Three-Pointed Star has succeeded in achieving something special.

In its perception of peerless quality and engineering, the W223 is striving to move forward and look back simultaneously to the glory days of the seminal W126 (1980-1991). This is through meshing traditional virtues like solidity and quality materials while dazzling its passengers with technology that is still friendly enough to want to enhance your experience.

You can sink into the soft lounge seats, watch the world pass by silently outside and never be aware of the road underneath or the engine ahead. Double glazing, exquisite and aromatic fabrics and materials and lush tactile surfaces work their magic inside the car, while an airtight and aero body, solid platform, air suspension and a muted yet muscular powertrain all do their thing underneath. The atmosphere is special and rarefied. That's what an S-Class needs to be and that's what is happening in our $299,000 (as tested) S450L.

The same more-or-less applies up front, as the same trim, leather, wood and technology surrounds the driver and passenger. The spectre of the car that is surely The Car of the Last Decade – Tesla's Model S – is evident in the portrait touchscreen and sparse, almost wallflower dashboard design and layout. No big imposing architectures here.

Yet, while the American upstart actually takes stuff away, the S-Class packs the cabin with subtle features that – like when the planes stopped flying last year and the birdsong subsequently returned – only become obvious once the cabin's design simplicity clears all the white noise for you to be in a better frame of mind to enjoy them.   

Take the haptic interface, for example, as it is perhaps the best we've experienced; the sense of well-being garnered from the cumulative effects of profound seat comfort (the massaging function was never switched off), cocooning micro climate environmental control, orchestral levels of audio entertainment and the theatre of light and vision performed by the two available screens; it is an automotive experience like no other. And the eye-tracking 3D-effect navigation set within the electronic instrumentation. No need for cinematic glasses to get the effect. The driving position itself, by the way, is also first class.

Room to stretch and grow for sure, and in every direction. But room for improvement? You betcha.

Your tester had a headache after a little while staring at that woozy 3D map. The central vents – four at the front, two in the rear – look and feel cheap, leaving us mentally redesigning them; they are frightfully out of place here; the carryover column-stalk auto lever should have been binned in 2005. And, even though the digital instruments have a number of options, none are elegant enough for the S-Class. That's an especially subjective criticism, clearly, but one that – in the context of classic Mercedes luxury sedan contenders – is justified given how timeless the Bruno Sacco era of Daimler design was. Look him up, kids.

Still, after a couple of hours behind the wheel, with our senses reset to calm, it is obvious that the S-Class cabin is a unique and wonderful place – as it should be at a cool quarter-of-a-million dollars.

Job done.

PS At 550 litres (20L more than before), the boot is massive and luxurious enough to sleep in.

Given the vast exterior dimensions and a weighbridge ticket the wrong side of 2700kg, it may come as a surprise to learn that the XM is strictly a five-seater with not even an optional third row.

That said, the uber-SUV Lexus LX in flagship, Ultra Luxury, trim offers just four seats in deference to the VIP clientele it’s pitched at, but also comes complete with reclining rear seats and a passenger’s side footrest which the XM can’t match.

Staying in the rear seat, there’s lots of legroom and plenty of space under the front chairs for feet. A lot of that is down to the wheelbase the XM shares with the BMW X7, and even behind a tall driver, there’s lots of space. In fact, compared with a BMW X5, there’s a full 150mm of extra legroom.

The pew itself flows into the door trims for a lounge effect which looks great with the contrasting light-coloured trim, and the centre arm-rest folds down to reveal a pair of cupholders. Extra storage space can be found in fold-out pockets in the rear of each front seat which also house a small, lidded panel that opens to reveal USB ports and power sockets. Dual-zone climate controls are also part of the rear-seat experience.

The gee-whizz stuff hasn’t been ignored, either, and the prismatic roof lining is nothing if not a talking point. But would a panoramic sunroof have been of more value to many buyers? The ambient lighting is a nice touch, too.

Up front, the view is dominated by the giant, twin curved animated dashboards. They deliver information and lots of it, to the point where it can almost seem a bit overwhelming.

The head-up display helps simplify things, but there’s absolutely no doubt there’s a lot going on in this cabin. Again, this is modern luxury motoring, but it remains that the menu system will take time to learn, even if the touchscreen function gives you an option on how you control things.

Multi-adjustable front seats are part of the deal and there’s an M-spec steering wheel which is heated. And although it features plenty of buttons, isn’t as daunting perhaps as the multi-spoked equivalent in some high-end AMGs of late.

The stereo system is also worthy of a mention, being a Bowers & Wilkins unit with roof mounted speakers and no less than 1500 watts of power. Digital radio is part of the package.

Even though it doesn’t offer a seven-seat option, luggage space in the rear of the XM is hardly class-leading. Cargo volume with rear seat up is 527L and 1820L with it folded.

Much of the wheelbase is devoted to rear-seat stretching room and although the batteries for the electric motor are positioned under the rear seat, the floor of the cargo area seems quite high.

The XM is one of those 'no options' vehicles. That is, you pay the basic price, you get one with the lot. The aged leather and even the optional 23-inch wheels and tyres are no-cost options, so it’s clear where BMW is aiming the thing.

As well as the plug-in driveline, all-wheel drive and all the M driving focus, the XM features plenty of tech including massaging front seats, heated seats all around, a high-end stereo, heated and cooled cupholders, four-zone climate-control, wireless phone charging and twin, curved info screens for the driver measuring 12.3 and 14.9 inches. The novel roof lining also features 100 pin-point LEDs for effect.

The cost of such detailing is a not insubstantial $302,200. That figure does, however, undercut two of its main rivals, the Lamborghini Urus ($395,888) and the Aston Martin DBX ($356,512).

It’s also worth mentioning that the XM is not even BMW Australia’s most expensive model; in fact, it’s fourth on the ladder.

Where are the V8s?

Right now, the only W223 you can buy is powered by an all-new 2999cc 3.0-litre in-line direct-injection six-cylinder turbo petrol engine dubbed the M256, complete with double overhead cams, an electric compressor intercooler and assistance from a 48-volt mild hybrid system and integrated starter-generator, adding 16kW and 250Nm to the 270kW of power at 6100rpm and 500Nm of torque from 1600-4500rpm.

The 9G-Tronic torque-converter automatic transmission and 4Matic all-wheel drive system combination is a first for the S-Class in Australia.

Top speed is limited to 250km/h, while the 0-100km/h sprint-time takes just 5.1 seconds in both models. Impressive for a two-tonne-plus luxury limo.

Here’s where the XM starts to justify its price-tag. While the use of an electric motor to boost a petrol engine has allowed some manufacturers to reduce the capacity of the latter, no such restraint has been shown for the XM. Instead, it gets the full 4.4-litre, twice turbocharged V8 that we’ve come to know and love from this brand.

It’s not that this is the engine’s first date with hybrid technology, but the mild hybrids that have come before it can’t match the XM for sheer brutality when both power units are unleashed.

The petrol V8 can muster up 360kW and 650Nm which, when boosted by the electric motor, jumps to a total of 480kW (combined) and 800Nm.

While the petrol engine drives through an eight-speed torque-converter automatic, the electric motor also drives through the transmission, an arrangement that is a bit different to some hybrids which use the petrol engine for the rear axle and the electric motor to drive the front wheels.

Of course, the requirement for the XM to feature permanent all-wheel drive, regardless of what power unit is running at the time, forces this layout.

Speaking of all-wheel drive, The XM’s version of BMW’s 'xDrive' layout has been specifically tuned for this vehicle and includes torque vectoring as well as a limited-slip rear differential.

The system has the ability to vary the torque split front to rear, with the default rear-bias giving a more sporting feel on good surfaces. An active rear differential also helps give the car a rear-drive feel.

As well as modes for 'Hybrid', 'Electric' and 'eControl' modes, the XM sticks with the M tradition of offering two M buttons which can be configured to set the parameters for steering, driveline, chassis and, in the case of the hybrid XM, the degree of braking regeneration offered.

Four-wheel steering is also part of the XM’s repertoire and, interestingly, there’s no air suspension here; just conventional steel springs.

But it does feature an electrically-adjusted anti-roll bar system which aims to strike a happy medium between what the driver wants and the road conditions demand.

With the aid of the mild-hybrid system, the S450 returned a combined average of an impressive 8.2 litres per 100km, which translates to 187 grams of carbon dioxide emissions per kilometre. 95 RON premium unleaded (or higher) is recommended. In the urban run it consumes 11.3L/100km (11.5 for S450L), and just 6.4L/100km (6.5 for S450L) in the extra-urban result.

At 76 litres, the fuel tank will allow a combined average range of about 927km between refills.

A 25.7kWh lithium-ion battery provides the power for the electric drive. It’s mounted under the rear seat and can produce a purely electric range of between 82 and 88km (based on WLPT test protocols).

Charge time from a conventional wall-box is said to be about four hours but, interestingly, the XM has no provision for DC fast-charging.

Fuel consumption (combined cycle) is an EV-typical 2.7 litres per 100km, which equates to a low 61g/km of CO2.

Once you’ve depleted the battery on a highway journey, expect the petrol V8 to consumer somewhere between eight and nine litres per 100km at cruising speed.

Using EV mode means zero-emission operation but, as with any electric car, how the power is generated to recharge it determines its real-world green-ness.

In former times, as the Germans say, a ‘450' on the boot indicated V8 power. In the W116 S-Class era it was one of the world's most evocative badges when ‘SEL' was also attached.

As mentioned earlier, though, it's the M256 3.0-litre turbo-petrol with a 48-volt ‘mild hybrid' electrical system that's doing the driving, to all four wheels. The real V8 W223 will probably surface later this year or in early 2022 with the S580L flagship. Bring it on.

This is not to say that S450 isn't good enough. With that electrified assistance, the blown straight six is smooth and swift off the line and rapid as the auto seamlessly steps up through all nine gears. Because it's so hushed and refined, it doesn't feel 5.1s to 100 clicks quick, but watching the speedo says otherwise – acceleration is assertive and strong right up way past the legal speed limit.

All that's missing is the burbling soundtrack of a classic Benz bent-eight. Oh well. Outstanding economy is a price we're literally willing to pay in lieu.

Even more impressive is the S450's ability to hustle along mountain roads like an overgrown sports sedan.

Now, for Australia, all S-Classes are fitted standard with an adaptive ‘Airmatic' air-suspension set-up, including air springs and self-levelling tech. In Comfort up to 60km/h, the ride height can be raised by 30mm, or lowered by 10mm under the standard 130mm baseline in Sport at any velocity, while in Sport+ it falls another 17mm.

With that in mind, yes, the standard air suspension performs a magnificent job smothering out most surface imperfections around town. Yet its real other party trick is to tighten up the chassis when corners get interesting and Sport mode is selected. Aided by progressively weighted and reassuringly responsive steering, the Mercedes tips into turns with precision and poise, slicing through with virtually no discernible body lean or understeer.

Now, we're not talking a leisurely drive on rural highways here, but Healesville's famous Chum Creek Road, where even a Porsche Cayman would feel like it's had a strenuous dynamic workout. The S-Class can be hurried along with confidence and finesse, displaying outstanding handling and roadholding for a 5.2-metre long limo. And the fact that the ride quality only suffers marginally when the red horns are out is all the more remarkable.

Back in the cut-and-thrust of inner-city peak-hour traffic, the Benz in Comfort mode continued to reveal its driver-orientated yet passenger-focused twin-personalities, zipping in and out of gaps while remaining comfy and composed inside.

Only when parking in tight spots are you truly aware that the W223 is longer than a Mazda CX-9. The optional four-wheel-steering system is claimed to slash the turning circle to A-Class hatchback levels. 10.9 metres is the claim.

The 2021 S-Class never ceases to amaze and delight.

While any M car is supposed to be rapid and dynamic, it’s also true that the over-arching perception of big SUVs is that they’re comfortable and plush. None of which explains the ride in the XM.

Regardless of how you fiddle with the settings, the ride is always brittle. Those big tyres with their minimal sidewall somehow manage to find every crack and join in the road, and it’s these sharp-edged imperfections that thump through to the cabin the most vocally.

It’s enough to make you wonder who this car is going to appeal to. Will it take to race tracks? Almost certainly not. So the whole point of these suspension settings might be a bit lost on some people.

Performance, meanwhile, is insanely rapid for something that could pass as a bulk carrier. The biggest giveaway to the mass is the transmission’s earnest attempts to keep everything moving by feeling a bit hyperactive on downshifts.

Using the ratios is always going to be the strategy, but with all that torque, maybe it’d be nice sometimes for the trans to hang on to a taller gear and let the boost blow it towards the next corner.

The sound track? Polarising. Even if it doesn’t convince you that Hans Zimmer (who developed the various electronically-synthesised noises the XM makes) should stick to winning Oscars, the augmented sounds are background noise rather than the main event here.

Even the petrol V8’s naturally stirring backing vocals have been electronically tweaked with debatable results.

That said, it’s nice to have something to listen to that isn’t the insistent tyre roar which becomes even louder on coarse-chip surfaces.

Steering effort is light but there’s not a lot of feedback in terms of actual feel. In fact, it’s borderline detached and only the sheer speed of the rack confers any athleticism.

Also, the rear steering seems to come in a few milli-seconds after the front has started to turn. And for all that all-wheel-steering agility, this is never a car that shrinks around you.

As well as the usual passive safety features, the XM also hides the latest active safety gear. In fact, BMW reckons the XM has more driver assistance than any other M car before it.

Those elements start with the 'Driver Assistant Professional' which bundles active cruise-control with stop-go ability, steering and lane-keeping control, automatic speed limit assist and active navigation.

Parking assistance is also featured which incorporates a reversing assistance function, front, rear and panoramic camera views with a 3D view built in.

BMW’s 'ConnectedDrive' includes an emergency call function in the event of a crash or other emergency.

No ANCAP assessment so far.

Unlike many luxury brands that persist with a sub-par three-year warranty, Mercedes-Benz offers a five-year/unlimited kilometre warranty.

Intervals are every year or 25,000km, with a capped price service plan starting at $800 for the first year, $1200 for the second year and $1400 for the third year, totalling $3400. Alternatively, there is a Service Plan starting at $2700 for the first three years (saving $700 from the normal capped-price service plan), $3600 for four years and $5400 for five years.

Like a lot of manufacturers, BMW knows consumers can be leery of EV tech when it comes to the cost of battery replacement. So, as well as the five-year/unlimited-kilometre warranty on the whole vehicle, there’s also eight years or 160,000km of cover for the high-voltage battery.

Servicing intervals are based on how the car has been used and it will inform the owner when a service is required.

A servicing package is included in the purchase price and BMW even throws in three years of roadside assistance.