IMHO, BMW has some of the best seats in the market today. MB is a close second. So you can't really go wrong. I have the comfort seats on my X5 and sport seats on my 540i/6. Personally I like the sport seats because of the better latteral support and better leg support but I think the sport seats on the X5 are not that same. Try both and see what you like and I'm sure you'll be happy with either seat.