I don't think there is any sensible comparison of the two. If your budget is 50k it shouldn't be anywhere near an F80 and if it's an F80 you want I'd want to be spending much less.
Maybe it isn’t a sensible comparison as such; I’d previously wanted an F80 and the opportunity arose this weekend. Upon being somewhat disappointed I then looked at the F90, as there was one there and it felt more inline with my expectations.
It’s maybe not the traditional approach to car buying where you have a set requirement and budget, but there you go.