I would choose neither. Go for something in between, half-glossy. Thats what I did with these style 199 on my old E90, and I will do this with my 403s as well.
http://db.tt/ELwXu2xP
http://db.tt/oeocMatG
100% glossy will look plasticy when clean, the matt just looks off n to dirty even when clean. As he said, they will quickly have a layer of dust on them them which will matte them out anyways.