Compare the Porsche 911 GT3 4.0 997 - [2011] vs Mercedes SLS 6.2 V8 AMG Coupe DCT-7 - [2009]. 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 GT3 4.0 997 or the Mercedes SLS 6.2 V8 AMG Coupe DCT-7. We'll leave it up to you to decide which is your favourite.