Compare the Porsche Cayman GT4 3.8 981 - [2015] vs BMW 3 Series M3 3.0 Bi Turbo G80 - [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 Cayman GT4 3.8 981 or the BMW 3 Series M3 3.0 Bi Turbo G80. We'll leave it up to you to decide which is your favourite.