I bet you'd prefer smaller, perkier tits to bigger, saggier ones. Big boobs always have a natural sag due to gravity (not necessarily for fake tits though). Seeing covered up or in a bra or bikini top hides the sag until they are unleashed. Smaller tits tend to not sag very much. And what I'm thinking is it's the sag you find disappointing once the tits you thought were going to look great, don't.