This article could so easily emerge as one part a description of the cars in question and four parts me wittering on about what makes a grand tourer and grand tourer, as though I'm an authority on the matter. Instead, I'm just going to tell you what they're like to drive and leave you all to make your own minds up (perhaps with a dash of me holding forth on the essential nature of a true GT car. Just to wrap things up).
McLaren reckons the new GT is a grand tourer - it even says so on the tin - which is why we've put it up against the two best GT cars on sale today. Because that's how group tests work. The thing about this new McLaren is that, on paper at least, it looks a lot like other McLarens. At its core you'll find the same basic carbon fibre tub that forms the backbone of every other series production McLaren, while the 4-litre twin-turbo V8 will be very familiar to existing McLaren drivers. Here it produces 620hp and 465lb ft of torque.
Rather than the trick interconnected hydraulic suspension arrangement that makes the 720S so freakishly capable, there are conventional springs, dampers and anti-roll bars, just like a Sports Series McLaren. As far as I can tell, the dashboard architecture is no different to that of a 570S, although a raised rear deck and a full-length tailgate means there's 420 litres of luggage space - albeit awkwardly-shaped luggage space - above and beyond where the engine rests.
At 1,530kg the GT is one of the heaviest McLarens yet produced, although that's still a relatively modest figure for a modern sports car with this sort of performance (0-62mph in 3.2 seconds, 203mph flat out). That's carbon fibre construction for you.
I can't bring myself to love the way the GT looks, mostly because it appears so much more substantial than any other Woking car. There's a visual weight to it that jars, especially given other McLarens look so lithe and athletic. And the chrome glasshouse trim is such a turn-off. But in the flesh the GT does have presence.
Parked alongside the Mercedes-AMG S63 Coupe, it seems absurd to suggest the pair might somehow be brethren. In fact, it is absurd - they could hardly be less alike. One thing I appreciate very much about the S63 is that to most onlookers it'll just be a Mercedes coupe. It could pass for a C200. Very few people will spot the quad exhaust tips and realise it's armed with 612hp and 664lb ft of torque. For covering ground at enormous speed without showing up on too many radars, the S63 might have every other car on the planet licked.
Its cabin is a triumph, more super-yacht than GT car. The dashboard layout is attractive, the seats probably the best in the business (as far as comfort is concerned) and the standard of fit and finish is exceptional. Nonetheless, I actually think the Bentley Continental GT V8 has marginally the better cockpit, mostly because there are clear signs all over the place of genuine craftsmanship - the gorgeous leather, the stitching, the wood veneer, the chrome plungers that open and close the air vents. Sitting in there is like being inside a country manor that's just been renovated by the Soho House hotel group.
The Bentley is a far flashier sort of machine than the Mercedes, of course. You'll not go unnoticed. We've chosen the entry-level V8 rather than the range-topping W12 because it's actually the better car. It's lighter by 50kg - all of that in the nose, helpfully - and with 550hp and 568lb ft, it's still colossally fast in a straight line. Four-wheel drive makes it far more sure-footed in low-grip conditions than both of its rivals here, too.
The Continental GT and S63 are both supreme grand tourers because they isolate you from the process of driving. You can spend hours at the wheel of either and not really be aware of time passing by. They're so comfortable and refined on the motorway that they make licence-losing speeds feel like 70mph. On balance, I think that's a good thing. Apart from their enormously comfortable chairs, both suppress wind and road noise beautifully and on air springs they ride serenely.
The Mercedes edges it in terms of comfort. Its ride is a shade more composed in the way it deals with bumps and ridges in the road, while its cabin quieter at a cruise. It makes driving relaxing, rather than taxing. Only in the company of the S63 can you find fault with the Conti's ride comfort or refinement, because in real terms it's up there with the very best in the world in both respects.
For me, however, the Bentley is the better grand tourer, and therefore the best GT car on sale today, because as well as being as relaxing as it is, it's also bloody good to drive along a twisty road - and I think some degree of agility is an important part of a grand tourer's constitution. This new model makes the previous Continental GT feel about as agile as a mahogany sideboard. There's balance, some adjustability, incisive steering, excellent body control... It's a far sharper thing to hustle through some bends than the 2,165kg kerb weight would have you believe.
It's searingly quick, too. If I had to guess, I'd say the official figures are very conservative, pegged back to keep W12 customers happy. Dig into the throttle pedal travel and at no point will you think, 'yeah, but another 90hp would be nice'. The 4.0-litre V8 twin-turbo is a fine motor, with very sharp throttle response and a bassy soundtrack when you want it, but also subdued refinement when you don't. Meanwhile, the twin-clutch gearbox works far better in this car than the one in the last W12 I tested.
On a dry road the lighter, more powerful S63 feels even faster still, but at this time of year the car is massively hamstrung by having only two contact patches through which to deploy all that torque. Again, the engine is a powerhouse and more or less flawless, except that whenever you tickle the throttle, you feel the rear boots spin fractionally and the traction control system leap into life while the engine is all but snuffed out.
What the S63 wins in terms of long distance comfort over the Conti, it loses on a winding hillside road. Its steering is completely numb by comparison, body control is a little sloppier and there's nothing like the same agility in direction changes. The Mercedes is far happier on flowing roads than contorted ones - on more open stretches, it holds itself together admirably well and does a reasonable impression of a sports coupe.
And the McLaren? Its cabin is airy and light, but nothing like as cosseting as the others'. The thinly-padded seats are sharply reclined, leaving your feet stretched out ahead of you, and although they offer lots of lateral support they don't let your tired body sink into them. On the move the steering wheel chatters endlessly to your fingertips, the rack tugging this way and that like an echo of the shape of the road beneath. Other McLarens do this even more; the engineers seem to have muted the GT's steering a little, but compared to a more conventional GT car there's still so much more texture flooding back through the rim of the wheel.
There is a fair amount of wind noise at motorway speeds, too, while the lightweight carbon tub acts like a resonance chamber, multiplying road noise and drenching the cabin in it. The brake pedal takes a deliberate shove, McLaren-style, to get any sort of response from the brakes themselves, while the ride quality is taut, connected and assertive, but never punishing.
You could cover a huge number of miles in the McLaren in a single day, but you'd arrive at your destination knowing about every single one of them. Its performance belongs to a different league to that of the other cars here, because with a fraction more power than the Mercedes but 500kg less body fat to battle against, it is sensationally accelerative. The engine itself still feels distinctly McLaren: nothing much happens beneath 3,500rpm, but the explosion from there to the redline is worth it. What's more frustrating is the hesitancy when you squeeze open the throttle on the way out of a tighter bend, because the little extra drive that you want to balance the car doesn't come...and it doesn't come some more...until BANG, when it all comes at once.
It's a very familiar sort of power delivery, then. In terms of response and linearity, though, it's far better than the smaller 3.8-litre engine used by other McLarens. The GT's twin-clutch transmission, meanwhile, is the sharpest and most responsive here, but also the fussiest in normal driving.
On a ducking and weaving B-road, the McLaren feels like a McLaren, only five or six per cent less so. Its steering isn't quite as detailed and there is a sense of mass higher up in the car, but by and large the GT spurts along between hedgerows the way a Sports Series model would. In that sense it's a thousand times more thrilling to drive than the Bentley, and more exciting than the Mercedes by a factor I can't begin to describe.
The McLaren GT is a very good car, then, but I just can't see the grand tourer in it. Apart from a somewhat awkward stowage compartment above the engine, it doesn't have any real advantages over any other McLaren as a long distance machine. In fact, I would argue that a 720S is actually more comfortable. The truth, as I see it, is that the McLaren GT is actually a supercar - just a slightly more usable sort of supercar.
What it isn't is a true grand tourer. It can't be, because a McLaren with a carbon tub, chatty steering, thin sports seats, a low-slung seating position and a boosty engine simply isn't the right starting point for a GT car. It's like setting out to make a supercar and using as your leaping off point a Mercedes-AMG S63 Coupe. In a nutshell, the best grand tourers isolate you from the process of driving, something the McLaren GT never does.
Anyway. I'll carry on being slightly flummoxed by the GT, admiring it much more as a driver's car than a long distance device. For what it's worth, I think the S63 is the most luxurious performance car you can buy right now, while the Continental GT V8 is simply the best grand tourer I've ever driven.
SPECIFICATION - MCLAREN GT
Engine: 3994cc, V8, twin-turbo
Transmission: 7-speed dual-clutch, rear-wheel drive
Power (hp): 620@7,500rpm
Torque (lb ft): 568@5,500-6,500rpm
Top speed: 203mph
SPECIFICATION - MERCEDES-AMG S63
Engine: 3982cc, V8, twin-turbo
Transmission: 9-speed automatic, rear-wheel drive
Power (hp): 612@5,500rpm
Torque (lb ft): 664@2,750rpm
Top speed: 155mph
SPECIFICATION - BENTLEY CONTINENTAL GT V8
Engine: 3996cc, V8, twin-turbo
Transmission: 8-speed dual-clutch, four-wheel drive
Power (hp): 550@6,000rpm
Torque (lb ft): 568@2,000-4,000rpm
Top speed: 198mph
Photos | Stan Papior