Compare the BMW 7 Series 750i xDrive 4.4 V8 Twin Turbo - [2015] vs Audi A3 RS3 Sportback 2.5 Turbo - [2015]. Find out which car is the fastest, most powerful, lightest or has the biggest engine in our top trumps style comparison page. Find out which car has the highest top speed or is the fastest accelerating, is it the BMW 7 Series 750i xDrive 4.4 V8 Twin Turbo or the Audi A3 RS3 Sportback 2.5 Turbo. We'll leave it up to you to decide which is your favourite.