Compare the BMW 6 Series 4.4 V8 Competition Pack - [2015] vs BMW 8 Series M8 Competition Cabrio 4.4 V8 Turbo F91 - [2019]. 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 BMW 6 Series 4.4 V8 Competition Pack or the BMW 8 Series M8 Competition Cabrio 4.4 V8 Turbo F91. We'll leave it up to you to decide which is your favourite.