Compare the McLaren 650S Spider 3.8 V8 Twin Turbo - [2014] vs Porsche 911 Turbo S Cabriolet 991 II - [2016]. 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 McLaren 650S Spider 3.8 V8 Twin Turbo or the Porsche 911 Turbo S Cabriolet 991 II. We'll leave it up to you to decide which is your favourite.