Compare the Porsche 9FF GT9 - [2008] vs Mercedes SLR Class McLaren Stirling Moss - [2009]. 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 9FF GT9 or the Mercedes SLR Class McLaren Stirling Moss. We'll leave it up to you to decide which is your favourite.