Which prompts the question: what do you test it against? Hundred-and-a-bit-grand luxury five-door coupés are, perhaps unsurprisingly, remarkably thin on the ground, as evidenced by the number of times you don’t see a Panamera on the road. The action for super-saloons with the kind of grip and handling we know the Porsche offers tends to take place below this stratosphere. I suspect a Mercedes-AMG E63 saloon would give the Porsche a hard time dynamically, if not from a luxury standpoint, but it hasn’t arrived in the UK yet. And contemporary luxury saloons tend to be just that: overdosed on luxury and undernourished dynamically for a test in this company.
Which means we’ve thought a little more broadly and make no apology for the fact that the Mercedes-AMG S63 Coupé you see here has two fewer passenger doors than the Panamera. Although the S-Class Coupé is shorter and lower than the equivalent saloon, its length is just half a centimetre shorter than the Porsche’s, while Mercedes-Benz has vast experience at making fourseat, two-door luxury cars, absurdly powerful or otherwise, and they’re mostly entirely satisfying.
This is one of those absurdly powerful ones. The S63’s 5.5-litre AMG V8 makes 577bhp, which it applies, via a seven-speed automatic gearbox, to the rear wheels only (a right-hand drive anomaly; in left-hand drive markets the S63 is fourwheel drive). There are air springs, whose functionality includes an active ride control system that can even tilt the body into a corner, and the asking price is £127,675.
Then there’s the BMW M6 Gran Coupé, evidence that even one of the definitive super-saloon manufacturers has had to diversify to keep pace with – or generate – market demands. Audi and BMW are the masters at this model expansion: first there was an executive saloon, then a two-door version of it, which these days then spawns an SUV, a convertible and, eventually a fourdoor ‘coupé’ like this one.
Underpinning the 6 Series Gran Coupé – it, too, is five metres long, albeit 4cm shorter than the Porsche – is the outgoing 5 Series platform, which also, in its time, sat beneath a 7 Series. We got in varying degrees of pickle over this platform: some 5 Series variants were best in class and some hardly recommendable, with curious ride and steering characteristics being chief among its problems, and the previous 7 Series never led its class.
Of everything on this architecture, then, over the years, I’ve found the M6 Coupé to be the most satisfying. Shorn of a need to ride with the accepted compliance of an executive or luxury car, it was allowed to be focused and taut, two things it pulled off rather well. Until today, I haven’t driven an M6 in four-door Gran Coupé trim, but at 1950kg, it is, encouragingly, the lightest of these three and also comes here fitted with BMW’s Competition Package, which raises the power of the twinturbo 4.4-litre V8 to 592bhp. Adding the Competition Package raises the price by £6300 to £101,965 but also stiffens the coil springs, dampers and anti-roll bars, a move that might lead you to think that the M6 will sacrifice yet more of the comfort that, presumably, it would be short of in this company anyway.
Well, you’d be half right, and we’ll come onto that. But it depends what you want your big super-saloon or sports sedan or whatever you want to call it to be, doesn’t it? And, at the risk of planting a mid-season spoiler in the box set that is this group test, that’s ultimately what it comes down to. These three are all terrific. I can’t remember the last time I wrote a group test of cars I thought were this capable, and yet so diverse in the way they perform ostensibly the same job.