Compare the Alfa-Romeo 8C Competitzione Spider - [2008] vs Porsche 911 Carrera 4 GTS PDK Cabriolet - [2014]. 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 Alfa-Romeo 8C Competitzione Spider or the Porsche 911 Carrera 4 GTS PDK Cabriolet. We'll leave it up to you to decide which is your favourite.