Compare the Porsche 911 Carrera S Cabriolet 997 - [2008] vs Bentley Continental GT Speed 2d Auto - [2007]. 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 Carrera S Cabriolet 997 or the Bentley Continental GT Speed 2d Auto. We'll leave it up to you to decide which is your favourite.