Compare the Mini Cooper John Cooper Works Roadster - [2012] vs BMW 6 Series 640d XDrive - [2014]. 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 Mini Cooper John Cooper Works Roadster or the BMW 6 Series 640d XDrive. We'll leave it up to you to decide which is your favourite.