Compare the Radical SR3 1.5 16V - [2001] vs Porsche 911 GT3 3.8 991 - [2013]. 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 Radical SR3 1.5 16V or the Porsche 911 GT3 3.8 991. We'll leave it up to you to decide which is your favourite.