Compare the Porsche Carrera GT - [2003] vs Alfa-Romeo 8C Competitzione Spider - [2008]. 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 Carrera GT or the Alfa-Romeo 8C Competitzione Spider. We'll leave it up to you to decide which is your favourite.