What's the difference?
Big sedans are not in vogue at the moment and huge luxury sedans were on the way down before the humble Commodore and Falcon departed the upper end of the sales charts. The Germans, who have always done a spectacular job of these flagship sedans, cheerfully persist with these cars.
Absolutely loaded with fascinating technology that bleeds its way down to the more mainstream models, they represent the zenith of the brand's innovation and style. The A8 is certainly that.
What it isn't, is particularly sporty, but after two years since its launch, V8 power has reached the fourth-generation super-sedan to deliver the latest iteration of the iconic S8.
Ever since the middle of the 1990s, I've been captivated by the Mercedes-Benz S Class. It used to be known as Sonderklasse - special class - and teenage me certainly thought it was. The one that caught my attention was the W140. A huge, two-tonne beast when that sort of mass was rare, it was loaded with amazingness and owned the road.
Part of its unique appeal was that that it was properly ugly. When it hove into view it was like a battleship entering Sydney Harbour. And it used almost as much fuel, with the V12 on board.
Over the years, genuine style has invaded the S-Class and today I found myself, for the first time, in an unusually pretty pair of S Classes - the S560 and S63 Coupes. And, astonishingly, it's the first time I've ever driven an S-Class. So with all that baggage I've built up over the years, they had a lot to live up to.
The S8's existence is a source of joy for me because it's not a huge SUV. Yes, it's a huge sedan but it's a reminder that the technological flagship is alive and well, at least in Germany. And the important thing about these cars is the way the toys filter down through the rest of the range. That used to take years but we're seeing this cool stuff a lot more quickly, right down to the A1.
The S8 punches, and punches hard in this rarefied part of an already shrunken section of the market - the twin-turbo V8 matches its German rivals, it's lighter and it's as well-stacked as any of the three. What it doesn't do, however, is shout about itself the way the other two do. It's the incognito choice.
Both of these vast vehicles are phenomenally comfortable - this is the kind of car that Mercedes does so well, and has done for decades. The S Class is rarely a disappointment but it's difficult to believe that such a big, heavy GT car can also dance the way the S63 does.
The S560 is far more weighted to being a GT - supremely comfortable with that active suspension, a growly, refined V8 and a cabin full of gadgets and comfort. The S63 is altogether more aggressive, to look at and to drive. Lopping the roof off both of them adds weight but, like any cruiser, also puts you out in the sun, the breeze and into your surroundings. Plus, in the case of the S63, you get more exhaust noise.
They're two very different cars and not just because of the engine. After all these years admiring it from afar, the S63 has delivered on my teenage expectations - fast, smooth and utterly mad.