Compare the Bentley Continental GTC 6.0 W12 Cabrio - [2005] vs Audi A6 S6 5.2 Quattro - [2006]. 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 Bentley Continental GTC 6.0 W12 Cabrio or the Audi A6 S6 5.2 Quattro. We'll leave it up to you to decide which is your favourite.