I've never driven an R-Class. Only sat into.
With the proper wheels (the 19", the same as the ML Pack Sport, for instance) it does not look bad. The front lights are a bit strange, ginving it a kind of surprised look...
It is not really good-looking either. It has a premium feel, a premium look, but it is not particularly attractive. The pics give a good idea of the car, only that it looks much longer and much higher than you imagine from the pics. It's quite big actually, especially the LWB of course.
I wouldn't take it in white, but it is mainly because here in Europe (especially in France) white is still uncommon for a private car. White here was the colour that only Sprinter, Transit and Traffic had, untill recently. Now it begins to change quite fast and you see more and more white cars.
So here my opinion is "geographically biased"
I only saw it in silver and black. I would take silver I think.
and for the interior, generally I like grey interiors. Black too, but I often prefer grey. I saw both in the R-Class, and both look good.
I don't really see any competition for the R-Class. The vans are far less luxurious and comfortable, whereas GL, Q7 and others are less roomy and less practical.
The interior is really impressive, clear and roomy, luxurious, very comfortable. The only problem of this car is really its van look. And the GL..
The GL looks much better imo, but is a more like a bigger ML. When you are inside, you don't really feel it is immensely vast. In the R-Class you do, it has a bigger legroom, headroom, everything-room.
I can't help you more, did not drive it...