Compare the BMW Z4 3.2 M Roadster 2d - [2006] vs Bentley Bentayga 4.0 V8 Bi Turbo - [2018]. 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 BMW Z4 3.2 M Roadster 2d or the Bentley Bentayga 4.0 V8 Bi Turbo. We'll leave it up to you to decide which is your favourite.