Compare the Porsche 911 GT2 RS - [2017] vs Audi A6 S6 4.2 Quattro - [1999]. 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 Porsche 911 GT2 RS or the Audi A6 S6 4.2 Quattro. We'll leave it up to you to decide which is your favourite.