BMW 6 Series vs Mercedes-AMG S63

What's the difference?

What happens when you struggle to sell an odd-bod, not-quite-a-coupe, sort-of-a-hatchback, almost-an-SUV model? Well, sometimes it gets axed, and replaced with a new model that bears a new name.

That's pretty much it in a nutshell for the BMW 6 Series Gran Turismo, which was formerly the 5 Series GT. It essentially takes the place of the 6 Series Gran Coupe - an alternative to the regular 5 Series sedan that's more attainable than a 7 Series limousine.

Confused? It's not as difficult as all that sounds - you just need to know that this model, the 2018 BMW 6 Series Gran Turismo, is supposed to offer a neat alternative to the go-to family luxury car or SUV.

I spent some time in the entry-level 630i to see if it can deliver on that promise. In fact, I spent more than 24 hours driving the BMW 6 Series GT over the past week, and I don't have a sore back, I haven't been left scratching my head over the intended purpose, I haven't been uncomfortable, and I haven't been left wanting for much.

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.