Compare the Porsche 968 3.0 Turbo - [1992] vs Mercedes SL Class 500SL R129 - [1989]. 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 968 3.0 Turbo or the Mercedes SL Class 500SL R129. We'll leave it up to you to decide which is your favourite.