The size isn't really that important to me, personally. Everyone loves a pair of good handful tits, but I'm equally turned on by someone like her:
http://www.sex141.com/en/gal-1046.html
Small tits, but still fun to play with - and a natural beauty to compensate for it.
As I said on here earlier, one of the best experiences I had so far was with Ada - she had small tits, almost not even a handful!