Compare the Porsche 959 Turbo - [1987] vs Mercedes GT AMG Roadster 4.0 V8 Bi Turbo - [2020]. 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 959 Turbo or the Mercedes GT AMG Roadster 4.0 V8 Bi Turbo. We'll leave it up to you to decide which is your favourite.