Compare the Porsche Cayman GTS 3.4L - [2014] vs Bentley Bentayga 6.0 W12 Bi 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 Porsche Cayman GTS 3.4L or the Bentley Bentayga 6.0 W12 Bi Turbo. We'll leave it up to you to decide which is your favourite.