leather all the way. BMW cloth never looks great, and ruins the executive looks of the inside of the car. Might as well buy a mondeo if you like cloth seats
on a serious note, i find with long distance driving that my back gets hot and perhaps a tad sweaty with cloth seats. I don't have this problem with leather, which seems to breathe better and feels more natural.
I have dakota lemon leather, and on a 7 year old car, with 65k miles on it, it still looks good as new: