[Wolfman64]

Sorry, this is only German and casually written at that, so likely not very Google Translate-friendly...

https://www.auto-motor-und-sport.de/...t-63-s-4matic/

Worth looking at the numbers.
M8 came in last while being the fastest (thin margin). AMG was better at the limit and the RS7 was slowest (speed & slalom) and longest braking distance.
But the car costs 1/3 less than the others while being fast and comfy, albeit with a high seating position...

Btw. I read in a different that switching the RS7 to 21" wheels makes it faster (well, not by much; 0.1sec). But still, there is a 58lbs weight difference between to 21" and 22" wheels...