Mercedes-Benz SL-Class vs BMW M5

What's the difference?

The SL's overall score is somewhat skewed by everyday concerns, and rules are rules - an average punter will find the price of this car somewhat confusing and the devil-may-care attitude to fuel consumption bewildering.

If neither of these things are a problem, then the SL63 makes plenty of - well, not sense, because it's not a particularly clever or considered car - but it fills a niche that not so long ago we all thought would go the way of the dodo.

The fact it sells so few examples is betrayed by some of the cabin amenities and the fact that Mercedes hasn't put much effort into reducing the car's weight to improve its consumption or sharpen up the handling.

The fact it still exists at all is pretty damn cool, though, and for certain people an SL63 purchase is the culmination of a lot of hard work.

If it is your dream car, the SL63 won't disappoint. Everyone who rode with me said it was mightily impressive, but you've got to really want it. When you're not far off buying a Ferrari California T or Aston Martin V12 Vantage S for the money, you'll need a real yearning for the three-pointed star to go this way. And if you do, good luck to you - you've probably worked quite hard to get here.

Let’s get one thing out of the way: the new M5 is a very good car. Considering the emissions limitations and size increase of its base model, it is an impressive bit of engineering. 

What’s trickier is deciding whether the new car is really better to drive. Less edgy but supremely comfortable and quiet; BMW leaned into the daily usability of the plug-in hybrid M5 rather than amping the petrol-electric system for maximum thrills. And do you know what? That’s fine with me. 

The new M5 still performs on road and track and does an incredible job of hiding its weight (most of the time). Perhaps the G90 is a little more Audi RS6 than F90 in its demeanour but some would argue that’s no bad thing. 

The concept of the BMW M5 is not static, it evolves with the times, and the G90 is no exception. Expect future Competition and CS variants to unlock some extra lunacy. 

Note: CarsGuide attended this event as a guest of the manufacturer, with meals provided.

The SL has always been completely unapologetic about its size and seems to be designed to accentuate rather than hide its length and width. The long bonnet screams power and prestige, and get out of my way, and is reminiscent of the little-loved McLaren SLR project of some years ago.

The size of the Mercedes logo on the huge front grille leaves you in little doubt about the brand of car that’s about to pass you at speed and some might say (okay, I would) that its large surface area is a little vulgar.

Like the SLR, the design doesn't seem to have a particularly cohesive strategy, with a number of Mercedes elements from around the traps that climb over each other. Roof up it looks awkward because of the gigantic posterior while with the roof down it looks overly long and, again, tail-heavy.

Folding hardtops are notoriously cumbersome and need a lot of room to hide them, but the silent operation is something to behold.

Elements that are worth deleting if possible are the dodgy 'Biturbo' badges. It's that kind of bling that gets people raising their little finger at you.

The M5’s raw size is what you notice first. The G90 M5 is a whopping 113mm longer, 67mm wider and 37mm taller than the car it replaces, with the wheelbase stretched 24mm.

It is also the most pumped M5 yet, compared to a 520i it is 70mm chubbier at its flared wheel arches. The ‘M5’ insignia on the C-pillar means you’ll know this is the fast one. 

Presence is not in question, then, but beauty? Not the right word. The G90 makes its predecessors — especially the original ‘E28’ — look demure. 

The cabin layout builds on the concept debuted by the iX electric SUV, with twin integrated screens and focus on technology and minimal buttons. Materials are mostly high quality and feel fitting for the M5’s asking price.

“Practicality” is about as relevant to this car as a code of ethics is to a drug dealer or a contract killer, because the SL63 buyer is hardly worried about cupholders and boot space. For what it's worth, there are four cupholders in the two-seater cabin (which might explain why owners aren't worried about their liquid carrying prospects) and a minimum boot space of 364 litres and a maximum - with roof up - of 504, which is actually not bad.

Cleverly, there's a little robot-operated luggage cover inside the deep boot that stops your gear from being crushed when the roof goes down.

There's also space in the long doors where you might secrete a bottle of wine that would get a NSW Premier fired if he thanks you for it, and a bin in the console to hide your phone.

BMW has persevered with its twin-screen, minimal-button approach for its 'Operating System 8.5' in the M5. 

The 14.9-inch central touchscreen is bright, responsive and high resolution but the software remains a little strange. The main interface is classy but when looking for settings to adjust you’re presented with a Windows 95-esque panel of small square touch targets. It’s not intuitive. 

Wirelessly mirroring Apple CarPlay or Android Auto works a treat, at least. Digital climate controls keep temp adjustment persistently on screen and a shortcut to fan speed. The nipple-like vent direction adjustment grows on you, as do the digital vent sliders. 

The 12.3-inch digital driver’s display still doesn’t have the freedom of customisation and clarity of Audi’s interface. 

The M5 has two cupholders, a deep central storage cubby, door bins that swallow two 600mL plastic bottles and twin wireless charging pad that resolutely grips smartphones even under the sort of tummy-churning G-Forces this M5 can manage. 

Setting the M5 apart from the regular sedan is a unique centre console bunching 'M Drive' modes, 'M Hybrid' modes and other shortcut functions together next to the gear toggle and M-engraved crystal 'iDrive' controller.

Comfortable front seats are power adjustable with in/out, up/down lumbar support and have two memory positions. 

The 5096mm long M5’s back seat is very spacious. Headroom is good for those beyond 182cm (six-foot), the bench is extremely supportive, while leg and toe room are adequate.

A fold-down centre armrest has two cupholders and there are USB-C charge ports in the back of each bucket seat for a total of four. 

You can buy an accessory mount that holds tablets or smartphones for rear seat passenger entertainment, too.

When you look in the boot, BMW offering a Touring version of the latest M5 makes even more sense. The load aperture is big but the usable space is narrow; the sides intrude on load space. 

The 466-litre space will make fitting suitcases for an airport run tricky and, even with the 40/60 split-fold rear bench, you will struggle to fit a bike in the back. There’s no spare tyre, either.

The last M5 was well equipped but the new car is wanting for nothing. Australian cars have just about every option for $259,900, before on-road costs.

Australian M5s wear staggered 20-inch front and 21-inch rear alloy wheels paired with standard metallic paint, 'M Carbon Exterior' package (including carbon roof and rear lip spoiler), adaptive LED headlights and BMW’s 'Iconic Glow' illuminated kidney grille surrounds. 

Keyless entry, a heated steering wheel, heated and ventilated front seats, interior camera, powerful 18-speaker Bowers & Wilkins sound system, M seatbelts, four-zone climate control and a power tailgate are the cabin highlights. 

Optional extras are thin on the ground; you can choose from (eight) no-cost paint colours and all manner of 'Individual' shades (from $4100), four interior trims including classy 'Dark Oak' wood and four leather colours. There’s classic black ‘Merino’ leather, or you can have it dyed with a mix of 'Silverstone', red or 'Kyalami Orange'. 

Aside from that, the only major option is carbon ceramic brakes at a staggering $18,500, and an M5 Touring wagon costs $263,900. 

Though the M5 is more expensive than Audi’s closest rival, the RS6, the gulf isn’t huge considering you get a lot more punch in the BMW. Mercedes-AMG does not have an E-Class answer, yet.

Good value, then? Well, an equally potent Porsche Panamera is twice the price. So yes, in a sense.

The SL63 is powered by Mercedes’ increasingly famous V8, with two turbos along for the ride to add oomph and cut the car's famous consumption, at least slightly. The 5.5-litre unit produces a massive 430kW and a scarcely believable 900Nm of torque.

All of that heads rearward via a seven-speed dual-clutch transmission that helps sling the 4.6m, 1848kg machine to 100km/h in 4.1 seconds.

Unlike the Mercedes-AMG C63, BMW has kept the M5’s eight-cylinder heart and this has proven to be a good decision. 

The 4.4-litre twin-turbo petrol engine has been optimised with “a cross-bank exhaust manifold and optimised oil separation”, says BMW.

The V8 spins to 7200rpm though it isn't a screamer, outputting a full-bodied 430kW (5600-6500rpm) and 750Nm (1800-5400rpm).

Augmented with a transmission-mounted 145kW electric motor that can produce up to 450Nm, thanks to pre-gearing, maximum combined outputs are 535kW and 1000Nm. 

Weight blunts punch, though, so despite nearly 100kW and 250Nm more, the new M5 is a tenth slower to 100km/h than its predecessor (claimed), at 3.5 seconds for the sprint.

You can thank a 220kW/tonne power-to-weight ratio, worse than the old car's 233kW/tonne figure. The new G90 claws some time back with brute force, hitting 200km/h in just 10.9 seconds and goes on to a limited top speed of 305km/h.

You can choose from five powertrain settings, starting with 'Electric' and 'Hybrid' for everyday use, while 'eControl' lets you store battery power for urban use.

'Dynamic' provides the best balance, says BMW, while 'Dynamic Plus' is like a qualifying mode. Think maximum combined punch for up to 10 minutes, at which point you’ll have drained the battery. 

Driving in pure electric mode, the take-off can be a little jerky but the quietude and decent power make it pleasant. Power sources are combined expertly in Hybrid and giving it some stick in Dynamic is more than enough to make your passengers feel queasy.

Much as is the case with the price, there's no real way to soften the blow here - the SL63 drinks like a footballer on Mad Monday, except it does it every day. The official combined cycle figure of 10.2L/100km is quite easy to double, as we did, averaging 21L/100km in mostly flowing suburban traffic. In the car’s defence, the accelerator pedal spent a good deal of time near the firewall.

The SL does have stop-start to help reduce its considerable environmental impact.

Electric-only range is rated up to 69km in WLTP testing, but the 18.6kWh battery is more likely to give you around 60km in real-world driving. It can be topped up in about two hours using an 11kW AC charger, or overnight on a three-pin socket. 

BMW includes both Mode 3 (public) and Mode 2 (home) charging cables with the M5. 

The M5 uses 3.2L/100km of 98 RON premium unleaded in ADR testing, corresponding to just 72g/km of CO2, so it should sail through the first rounds of Australian emissions regulations. 

Indulging in what the V8 has to offer sees that consumption spike, though. An enthusiastic road drive saw the M5 gulp 12.4L/100km, according to the trip computer.

There are a number of impressive things about the way the SL drives. Firstly, astronauts will be familiar with the galactic thrust of the V8. It seems endless, seamless and ready to sling the big coupe into the outer atmosphere. Few engines of any kind can match the relentless go on offer in the SL and much of the credit should go to the seven-speed twin-clutch transmission.

When you jump on the brakes and shift down, the exhaust keeps the show going with angry crackles and pops.

Containing a torque figure like the twin-turbo V8's requires a lot of electro-trickery to stop you from being launched off the road. The great thing about all that stuff is that it works unobtrusively and smoothly.

Mashing the carpet in an SL without traction control would create much sound and smoke but little forward progress, such is the twist on tap. The SL has a range of modes from full-nanny (which is meant to keep you on the slippery Alpine road you've chosen to get you to some Swiss ski resort) while turning the dial all the way around to Race loosens the bonds.

It's in this mode you'll have the most fun and it does seem that the intermediate settings are a bit of a waste of time. Race mode does little to diminish the amazing ride quality provided by the active suspension setup, but relaxes the reins on the huge rear tyres. Exiting roundabouts is suddenly a huge laugh, with the tail cheerfully breaking traction and the two-mode exhaust thundering in a most pleasant way.

Better still is that when you jump on the brakes and shift down, the exhaust keeps the show going with angry crackles and pops, with more on the way when you lift off. There's little to match the aural pleasures of a properly tuned V8 and Mercedes has resisted the temptation to quieten it down on the outside and generate a fake noise for the inside. Although that would be stupid in a convertible, if you think about it.

The SL63, despite its AMG badge, isn't about all-out handling, of course. The Ferrari California would definitely show it how it’s done on a winding country road. The SL is more about flow, building momentum and rarely shifting down to second gear. The monstrous torque is enough to keep things rolling but should you wish for a bit more of the exhaust bellow, second is there for the taking.

Hustling the big convertible feels wrong, not because it can't do it, but because it's not really what it's for. Having said that, it offers a kind of fun that nothing else on Earth will provide, not even a Bentley GTC.

With the roof up, the SL63 is a quiet place but not remarkably so. The huge sticky tyres do the cabin's hush no favours, with an annoying roar on a wider range of surfaces than you might expect.

Roof down, it's hardly a paragon of virtue. A lot of wind noise reaches the cabin, even well below the huge speeds the SL can reach. So if you want to talk, it's windows up you'll need to deploy the mesh screen that bridges the roll hoops.

The three M5 elements start with daily usability. We trundled out of Bathurst in electric mode, with the adaptive dampers (and other myriad settings) in Comfort. 

The M5 has steel springs, double wishbone front suspension and a five-link rear axle, all of which has been heavily reworked by the boffins at M. Naturally, the ride is firm, though in Comfort the body moves through its motions smoothly. 

The M5 is an effortless tourer, its eight-speed automatic shmoozing through ratios as it climbs and descends steep gradients. Wind and tyre noise insulation is good on coarse chip tarmac, though a bit more burble from the V8 would be appreciated. 

The M5 has nine adjustable parameters to wake it up: 'Drivetrain', 'Energy Recovery', 'Drivelogic' (gear shift aggression), 'Chassis', 'Steering', 'Brake', 'M xDrive', stability control settings and 'M Sound'. Favourite settings can be stored to the wheel-mounted M1 and M2 buttons. 

With the dampers still in Comfort the M5 remains fantastically capable with power delivery from the xDrive mighty rewarding on corner exit. Sport dampers sharpen the experience up further, amplifying the M5’s surprising agility. Thank the rear-wheel steer for this big sedan’s switchback performance. 

Step beyond the limit of grip, brake too late, or get on the power too early, though, and the M5’s mass reveals itself rapidly. It doesn’t help that the accurate steering is devoid of feel. The brake-by-wire pedal is too numb and light, as well, making it tricky to judge grip levels on the road.

Feel is less of an issue on a dry Mount Panorama circuit, where the M5 turns out to be a total pussycat. The all-wheel drive, consistent dynamics, strong brakes and well-tuned stability control make for an approachable but seriously fast sedan.

The responsive transmission will hold gears to redline and is eager on the downshift in its most aggressive setting while tactile shift paddles make commanding ratio changes yourself that bit more engaging. 

Prodigious punch out of corners is matched by the impressive consistency of the carbon ceramic brakes. The M5 pulled up for The Chase every time with minimal fuss, even from above 250km/h.

Similar credit goes to the 285mm front and 295mm rear Hankook S1 Evo tyres which remained consistent and predictable all day despite reaching temperatures over 130 degrees, according to the tyre pressure monitor.

The regular BMW 5 Series range scored a maximum five stars in 2023 ANCAP safety testing but this does not apply to the M5.

The M5 features nine airbags and a host of active safety systems, including auto emergency braking (AEB), blind-spot monitoring, rear cross-traffic alert, lane-keep assist, auto parking and speed limit assist. 

Lane-keep can easily be turned off via two taps but the other systems require more menu navigation, though are mostly unintrusive. A 'Track' mode disables lane-keep, AEB and other systems along with switching the central display off. 

The SL63 is covered by Mercedes' three-year/unlimited kilometre warranty. And, er, that's it.

In Australia, BMW has moved to match other manufacturers in offering a five-year/unlimited kilometre warranty on all its cars. 

Servicing is recommended on a condition basis, with the M5’s multimedia system prompting a visit to the mechanics. BMW offers pre-paid service packs for five years/80,000km at a price of $5059 for the basic offer and $8152 for 'Inclusive Plus', which covers brake pad and rotor replacements. 

It is expensive next to a regular 5 Series but when you consider the purchase price and performance level, the M5’s service pricing is not astronomical.