Well after some extensive research at
FlashYourRack.com, I can conclude that the most popular breasts are medium-large in size, and, in general, the perkier the better (extremely obvious implants were rated above average, scoring higher than naturally big breasts). Although to be fair, almost none of the photos I saw were actually rated below about 3/10. Which just goes to show that, in the greater scheme of things, all boobs are good boobs. (P.S. a lot of these girls are flashing a bit more than their rack, which may or may not be affecting their scores)