I like big butts, but toned ones that are big from working out and absolutely hate fake ones. I tried to figure out why, since I love big fake boobs. And I think it's because butts are muscles, and you expect them to have a certain flow and be connected to other muscles. They aren't just protrusions that stick out from a mostly flat surface, like breasts are. So when a girl has a big butt, you also expect her to have developed thighs and hamstrings to go with it, and when that's missing, it looks like they're wearing a diaper below their skin. With boobs however, you're just making the already present protrusions bigger and rounder, so you don't get the feeling that something's off.