Compare the Ford Sierra RS Cosworth - [1986] vs Cadillac CTS 3.6 V6 Sport 4d Auto - [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 Ford Sierra RS Cosworth or the Cadillac CTS 3.6 V6 Sport 4d Auto. We'll leave it up to you to decide which is your favourite.