Droptop battle: Mercedes-AMG SL63 vs Bentley Conti GTC vs Porsche 911 GTS Cab

Mercedes has an embarrassment of riches in this department, being the company that got a head start on the competition by inventing the car. The S-Class. The G-Wagen. And the SL. Doesn’t matter if you’re thinking about a luxury limousine, a rugged 4x4 or a sporting GT: there’s a Benz of yore among the greats.

A cloud of confusion hovers over the new, seventh-generation SL. Is it now a supercar, or still a golfer’s boulevardier? Is it a heatseeking muscle car, or a topless S-Class? That’s why we’ve flanked it with a sweet spot 911 Cabriolet (the rear-wheel-drive GTS) and probably the best Bentley ever made: the GTC Speed. In other words, the best sports car all-rounder money can buy right now, and one of the all-time great grand tourers. We have our bookends. Now to see where exactly the new SL lies in-between them.

Photography: Jonny Fleetwood

That’s the Mercedes-AMG SL63 4MATIC, to address it by its full name. Lots of clues here that this is a car that’s been pointed in a very different direction – and towards a very different kind of customer – than the last half century of ancestors. Not least the look of it, all brooding toothy menace and hunkered down stance. It makes the 911 look unimaginative, and the Bentley tall and portly.

And yet somehow, the more you look at it, walk around it, and follow it up the road, it’s lacking something. The face could be from a CLS, or a CLA. It’s as bulbous as the Porsche at the back, but without the excuse of housing a rear-mounted engine. Prettier than the last couple of SLs? Undoubtedly, but not quite knuckle-bitingly gorgeous. Maybe it’s the Audi-cliché primer grey paintwork.

Underneath, it’s now an in-house project designed and built by AMG, like the old GT and the SLS gullwing models were. This isn’t a Benz that’s been breathed on after the fact. AMG specified the all-new, all-aluminium platform ready to underpin a fresh GT two-door flagship.

The foundations are massively stiffer and lighter than any SL before it. As you can see, the folding hard-top familiar since 2001 is gone, and a canvas roof is back. Lighter, easier to package.

The SL63 badge is back too, denoting a thunderous, cackling V8 twin-turbo developing 577bhp. So they say.

Feels more like 650, maybe 700bhp from the way it rampantly chews through the short-ratio nine-speed gearbox and hurls you up the road with a ruthless efficiency alien to the wayward old AMG GT Roadster. That’ll be the last element of the unwieldy name coming into play: the 4MATIC all-wheel-drive system. It’s fabulously unobtrusive, mediating where the engine’s fury is sent without showing its working in the margins. You demand speed. You summon the noise. The traction control light doesn’t even blink. A moment of turbo lag, and POOF. You’re in the Peak District.

Actually, I came up in the Bentley, which was fabulous and expensive. It sits imperiously in the outside lane, devouring distance, massaging my back, the thickset canvas toupee cocooning me in warmth and peace. Out from behind another train of trundling lorries and ah, yes, speed camera. Lifting off doesn’t do much when you have the momentum of an express train, to match the distant W12 drone that sounds like a Deltic locomotive. Yes, I appreciate the irony of being nicked for speeding in a car literally called ‘Speed’. In my limited defence, 80mph in one of these offers as much sensation of velocity as 580mph in a Dreamliner.

The Speed is Top Gear’s favourite current Bentley because it now has a raffish, naughty streak as well as the opulence and comfort you expect. The extra horsepower is meaningless, but there’s a rear differential willing to swing huge wads of torque at the rear. The result is an outrageous yet benign ability to four-wheel drift 2.3 tonnes of steel, leather and stone. Yes, stone. This GTC has the optional stone veneered dashboard. As if you needed your Conti to feel even more solid, now it’s got a church facade either side of the rotating touchscreen. Gloriously silly, but also hugely endearing.

Ultimately, when you arrive at the A- and B-roads that nestle around the base of Mam Tor, the Bentley can only keep up the pretence of being a sports car for so long. Without optional ceramic brakes the left pedal goes worryingly spongy after a couple of heave-ho stops, and Bentley’s never quite got on top of this car’s Achilles heel: the eight-speed twin-clutch gearbox. It’s fine in the less torquey V8s, but with the limitless potency of the 6.0-litre engine to manage, it forgets its manners, dithering then guessing and snatching at gears. In the Conti, the most satisfying kick up the rear comes from the ‘wave’ massage function. Or was it ‘pulse’?

No, if you want a drop-top with a decent boot that can corner, you want a proper sports car. The Porsche. Obviously. How many times have words to that effect been written in head-to-heads over the decades? Which makes it all the more intriguing why AMG has gone so decidedly sportish with the new SL. It’s firmer than the 911, yet lacks the Porsche’s impeccable body and wheel control. It’s got faster steering than the Porsche, without any of the 911’s feedback or poise. And the 911 has the audacity to do without four-wheel drive and still it’s got traction to spare. Yet when you overcome it, it’s beautifully predictable. Sure, a bang-on SL63 rival is the AWD 911 Turbo. But this isn’t about rivals, remember, it’s about bookends. The GTS is yet another 911 that does more with less. You won’t find a more crushingly complete car. It’s even an assured cabriolet, especially with the electronic wind deflector motored upright.

When you’ve got a 911 skulking around being tediously excellent across the board, some of the SL’s design decisions wilt in the heat. Take the packaging. Mercedes has very deliberately tried to morph the SL into an unapologetic sports car, then stuffed in token rear chairs just as cramped as the 911’s.

The front thrones still massage your knotty back as you rumble about, while wafting comforting warm air around the nape of your neck. So there are still hints that this car is a big woolly jumper, for people who like wearing big woolly jumpers.

But no one over the age of 15 has a cat in hell's chance of operating the SL's disastrously unhelpful interior. It’s like a greatest hits compilation of everything we detest about modern car cabins. Fiddly touch-sensitive pads on the three-spoke steering wheel? Check. All major functions entrusted to a fingerprint- smeared touchscreen? Oh yes. More ambient lighting options than helpful features? Yep.

The very fact Mercedes has motorised the touchscreen to change angle depending on sun glare should’ve hinted to headquarters they were engineering their way out of a design dead end. The screen gets worryingly hot even on a brisk winter’s day – those processors are working really quite hard to do the job a button would be better at.

Then there’s the driver’s instrument screen. Eight different displays to choose from. Above, seven varieties of head-up display. It’s bafflingly complicated and – criminally – makes the SL feel cheap inside. Instead of knurled metal switchgear, it’s red-hot pixels.

It’d be nice to feel like the interior hadn’t been set up like an escape room

Even popping that canvas roof down is accomplished by fingering a slide to unlock-style gimmick in the touchscreen. If your hand is momentarily deflected as you drive along, the roof operation stalls. After two days I accidentally discovered you can double press and hold the roof button to move the roof. Does the 11.9in screen find space to tell you this hack? It does not.

Yes, it’s basically all carried over from an S-Class. But an S-Class is an easygoing deluxe barge. The SL63 is a missile. When you’ve got almost 600bhp and 600lb ft of torque on tap, Ferrari-quick steering in your hands and an alarmingly firm ride under your bum, it’d be nice to feel like the interior hadn’t been set up like an escape room, brimming with puzzles, calculated frustrations and devious dead ends.

It’s certainly not a GT car: there’s more road noise from the fat tyres, and the soft-top isn’t as well insulated as the GTC’s thickset canvas toupee. It’s also too firm to be a cruiser. It’s as though AMG was so proud of how stiff the new SL’s aluminium structure is, it wanted to show off how taut it could make the ride as a result.

Even in Comfort mode the SL63 is busy, and dialling it up through Sport to Sport Plus pours quick-setting concrete into the dampers. AMG’s debuting a new McLaren-style anti-roll bar free system on this car, employing cross-linked hydraulic lines to ensure control and support while supposedly allowing a more fluid ride, but the SL is fidgety and distracted. Fitting hyperfast wrist-flick steering with no feel or feedback only increases the sense the car’s being bullied by the road, instead of breathing with it.

So it’s too frenetic to be a loping grand tourer, too disjointed to be a Porsche 911-rivalling sports car, and too complicated to be operated by anyone. In character then, it’s ironically close to the old AMG GT.

Perhaps the SL is best thought of as a replacement for the raucous old AMG GT Roadster. Fine. Gotcha. Except, why badge it as an SL? That adds baggage and a history this car is totally at odds with.

So the 911 wins. Well yes, except it’s not quite that simple. It’s by far the best car here to drive. But it doesn’t make the best noise (Merc) or have the most commodious or opulent interior (Bentley). If you want a machine that makes every journey feel like a state visit, the Continental is magnificence on wheels.

The SL is closer to the 911 on the spectrum, but loses out to a much less expensive Porsche as a drive, and a piece of common sense. It serves to prove that reinventing an icon for a new audience really ain’t easy.

VERDICT

1: Porsche 911 GTS Cabrio [9/10]

The least head-turning car, but a brilliant all-rounder. Even rather good value for money

2: Bentley Continental GTC Speed [8/10]

Tripped up by its lazy gearbox, but what a way to travel. The only true four-seater here

3: Mercedes-AMG SL63 [6/10]

A schizophrenic effort: amazing powertrain meets clumsy chassis and horrendous interior