Compare the Lamborghini Diablo GTR 6.0L V12 - [2001] vs Alfa-Romeo 156 2.5 V6 - [1997]. 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 Lamborghini Diablo GTR 6.0L V12 or the Alfa-Romeo 156 2.5 V6. We'll leave it up to you to decide which is your favourite.