Let me first point out that although most of these girls are small, there are a few here that are firmly in the medium category. Oh well, it is the BEA.
But I've always thought that size gets a girl the majority of her points for having an attractive chest, but with a lack of mass she could still make up for some of it with a nicely shaped chest. Most of the girls on here have that great shape and I think are quite sexy. With that said, there is only so much shape can do, even if it is perfect, and I will still prefer larger in almost all cases. There is a also a bottom end, where a girl is so small her shape is irrelevant, and her chest is just not attractive.