Compare the Audi A8 6.0 W12 SWB Quattro D3 - [2004] vs BMW 4 Series M4 Convertible F83 - [2017]. 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 Audi A8 6.0 W12 SWB Quattro D3 or the BMW 4 Series M4 Convertible F83. We'll leave it up to you to decide which is your favourite.