Elongated is better, and I'll tell you why. The elongated ones look handsomer and they are much more maneuverable and active in every way. The round ones are also kind of cute, admittedly, but they lie around too much and are dead lazy! They expect you, fer Chrissake, to bring the water dish to them when they get thirsty! You will sometimes find that the elongated ones get a lot rounder as the years go by. This can be prevented to some extent by restricting their food supply and taking them for a brisk walk every day, but there's no guarantee that you won't end up with a very round one eventually, in which case you can use it as a doorstop.