Well, usually i would go for 256, but again, i am not a guy who will have 100gb of Music or Movies,
i only listen and watch a selective songs and movies, i have a Desktop with 3TB to store my whole movies and songs
so i will go for 128gb for the sake of the price, because what i usually store on my Laptop are only work and a couple of music Albums and 2 or 3 games and maybe dual OS, which 128 is, i think, the most perfect selection