Mercedes-Benz GLS vs BMW XM

What's the difference?

The GLS63 is an intimidating beast from afar, but it rewards its occupants in almost every way. Yep, there really isn’t a box it doesn’t tick without serious compromise, such is its breadth of capability.

If there was ever a Swiss Army Knife of cars, the GLS63 is definitely a contender for the title, one that makes it very hard to wipe the smile off your face. Just make sure you can fit it in your garage first…

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.

If the GLS63 was a Marvel superhero, it would undoubtedly be the Hulk. Simply put, it has road presence like few others. In fact, it’s frankly menacing.

Of course, the GLS is already pretty intimidating due to its sheer size and blocky design, but the GLS63’s full-fat AMG treatment takes it to another level.

Naturally, the GLS63 gets an aggressive body kit, with its purposeful bumpers, side skirts and rear spoiler serving as instant reminders of what you’re dealing with, but it’s AMG’s signature Panamericana grille insert that really hammers home the point.

Around the side, the GLS63’s 22-inch alloy wheels with staggered tyres (front: 275/50, rear: 315/45) make their presence known, positioned below the wheelarch extensions.

That said, some fun’s also had at the rear end, where the GLS63’s diffuser element integrates the foreboding sports exhaust system with quad tailpipes very neatly.

The focused Multibeam LED headlights also look the part, while the opposing LED tail-lights tie everything together outside quite nicely.

Inside, the GLS63 stands out from the GLS crowd with its sports steering wheel with Dinamica microfibre accents, and multi-contour front seats, which are covered in Nappa leather alongside the armrests, dashboard and door shoulders and inserts.

Of note, the doors bins are unfortunately of the hard plastic variety, which is very disappointing in a vehicle that costs this much. You would expect that cow hide would also been applied to them, but alas it isn’t.

The GLS63’s black headliner serves as an obligatory reminder of its sporting intent, and while it makes for a dark cabin, metallic accents are prominent throughout, while the optional trim (our test vehicle had carbon-fibre) mixes things up, alongside the ambient lighting.

And let’s not forget the GLS63 is still loaded with plenty of cutting-edge technology, including a pair of 12.3-inch displays, with one the central touchscreen and the other the digital instrument cluster.

Both are powered by Mercedes’ class-leading MBUX multimedia system and feature Apple CarPlay and Android Auto support. This set-up arguably remains the best there is today thanks to its speed and breadth of functionality and input methods.

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.

Measuring 5243mm, 2030mm wide and 1782mm tall with a 3135mm wheelbase, the GLS63 is an upper-large SUV in every sense of the term, which means it’s also very practical.

For example, cargo capacity below the load cover is decent, at 355L, but stow the 50/50 power-split-folding third row via the boot and it’s very good, at 890L, or drop the 40/20/40 power-split-folding middle bench, too, and it becomes a cavernous 2400L.

Better yet, the boot’s aperture is almost square, and its floor’s flat, while there’s no load lip to contend with, making loading bulkier items even easier. Up to four tie-down points are also on hand (depending on seating configuration) to secure loose cargo.

Under the false floor is the space-saver spare, which is to be expected, but what isn’t expected necessarily is the fact there’s also enough room there for the cargo cover when it’s not in use, which would be the case if six or more passengers are regularly onboard.

Moving into the power-sliding second row, the GLS63’s practicality is once again brought to the fore, with up to six-plus inches of legroom available behind my 184cm driving position.

There’s also two inches of headroom with the panoramic sunroof in situ, not to mention just enough toe-room. The GLS63’s small transmission tunnel and sheer width also mean three adults can be seated on the middle bench with few complaints.

Amenities-wise, the second row has map pockets on the front-seat backrest and a small fold-down cubby below the rear climate controls, with it containing two slots for smartphones and a pair of strategically placed USB-C ports.

The rear door bins can take one large bottle each, while a fold-down central armrest is also on hand, featuring a shallow tray and retractable (and flimsy) cupholders.

Alternatively, the $2800 Rear Seat Comfort Package fitted to our test vehicle subs in a tablet that can control the multimedia system, a wireless smartphone charger and a small cubby into the former, as well as a heated/cooled cupholder atop the rear of the centre console.

In the third row, it’s not quite as roomy if you’re an adult. With the middle bench in its most accommodating position, my knees still brush up against its backrest, which is to be expected given it’s primarily designed for children. I also have an inch of headroom there.

Nonetheless, getting in and out of the third row is relatively easy as the power-operated middle bench tumbles forward and provides just enough space to make entry and exit somewhat graceful.

When seated, rear occupants are treated to two USB-C ports and one small cupholder each, so they’re arguably taken better care of than those in the middle.

Child seats are well and truly accommodated, with four ISOFIX and five top-tether anchorage points fitted across the second and third rows, although the latter will inevitably prove to be a much tighter fit.

The driver and front passenger are still taken care of, with a front cubby taken up by two heated/cooled cupholders, a wireless smartphone charger, two USB-C ports and a 12V power outlet, while their door bins take one large and one small bottle each.

In-cabin storage options include the large central storage bin, which hides another USB-C port, while the glovebox is on the smaller side, with about a third of it taken up by the fragrance, which is pumped into the cabin to ensure the interior always smells its best.

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.

The GLS63 is powered by a familiar 4.0-litre twin-turbo V8 petrol engine, with its version producing a thumping 450kW of power at 5750rpm and 850Nm of torque from 2250-5000rpm.

This unit is mated to a nine-speed torque-converter automatic transmission and AMG’s fully variable 4Matic+ all-wheel-drive system with torque vectoring and a rear limited-slip differential.

This set-up also features Mercedes’ EQ Boost 48V mild-hybrid system, which actually gives a 16kW/250Nm electric boost in short bursts, such as when accelerating off the line.

Speaking of which, the GLS63 sprints from a standstill to 100km/h in just 4.2 seconds, while its top speed is electronically limited to 250km/h.
 

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.

The GLS63’s fuel consumption on the combined-cycle test (ADR 81/02) is 13.0L per 100km, while its carbon dioxide emissions are 296 grams per km. All things considered, both claims are unsurprisingly high.

In our real-world testing, we averaged a fearsome 18.5L/100km over 65km of driving, split between highways and country roads, so not your usual mix. A very heavy right foot definitely influenced that result, but don’t expect to do too much better in a normal run.

For reference, the GLS63’s 90L fuel tank can be filled up with 98RON petrol at a minimum.

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.

Frankly, the GLS63 has absolutely no right being as capable as it is. It’s a really big bus that’s legitimately convinced it’s a sports car half its size.

Being a GLS variant, the GLS63 has independent suspension consisting of four-link front and multi-link rear axles with air springs and adaptive dampers, but its party trick is the addition of active anti-roll bars.

In what feels like magic, the GLS63 is simply not intimidated by corners, despite having massive dimensions and a considerable 2555kg (kerb weight) to deal with.

The active anti-roll bars make the GLS63 so much easier to drive fast through the twisty stuff, almost eliminating body roll, taking one key variable out of the equation for the driver. Active engine mounts are also fitted, helping to settle things even further.

The electric power steering on hand is also good. It is speed-sensitive and has a variable ratio, which basically makes the set-up more direct when it needs to be. It’s typically light in hand, too, until one of the sportier drive modes is engaged and extra heft is added.

So, handling is scarcely believable, which means the ride must be compromised, right? Yes and no. With the adaptive dampers in their softest setting, the GLS63 is very compliant. In fact, we’d say it feels luxurious when compared to other high-performance SUVs.

That said, our test vehicle was fitted with the optional 23-inch alloy wheels ($3900), which look the part but expose sharp edges and other road imperfections, not to mention generate noise easily heard inside. Naturally, feedback is exacerbated in the sportier drive modes.

Anyway, there’s more performance, and the GLS63 has the rest in spades. Its engine is a powerhouse in every sense of the word. It’s so powerful, in fact, that it hilariously hunkers down off the line or when suddenly accelerating at low speed.

Thanks to the mild-hybrid system, wads of torque is available from the get-go, making for a highly responsive driving experience, even in those rare moments when the engine isn’t on song.

While not as characterful as some of the other members in the 63 series, the GLS63 still makes some thoroughly entertaining noises, with its sports exhaust system popping like mad while on the overrun.

All of this ability is very well and good, but you need to be able to pull up quickly, and the high-performance braking package (400mm front and 370mm rear discs with six-piston fixed callipers and single-pot floating stoppers respectively) mercifully does exactly that.

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.

As with all Mercedes-AMG models, the GLS63 comes with a five-year/unlimited-kilometre warranty, which currently sets the standard for the premium market. It also comes with five years of roadside assistance.

The GLS63’s service intervals are relatively long, at every 12 months or 20,000km (whichever comes first). Better yet, it’s available with a five-year/100,000km capped-price servicing plan, but it costs $4450.

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.