I've just been to the dealer, my opinion is to go for leather if budget is not so tight, the leather is such good quality, very soft on the surface, but supportive! the sales agent told me bmw use the same leather matherial from the 6 series and the stiching quality is first class. you will be spending a lot of time in your new baby, so don't do something you will regret.
I would't say audi has better leather finish, is nice, but in terms of feeling, audi seats are little bit too hard, infact both are very classy finish. (my brother owns an audi a4 with leather)