For me, its all about the squish, whether it's rounded, lumpy, in several rolls, nothing is better than pressing into squishy fat. I used to get turned on making pizza dough because of this!
They can be both very beautiful, but at extremely large sizes the double belly starts to have clear advantages. It can poke out further forward, making the body look much rounder, while after a certain size a single belly only grows downwards, looking flat instead of round.