Breed quality?

I noticed in alot of Bostons, where their chest is white, it's completely white. Smudge's belly and chest are speckled with black spots. Does this have to do with the quality of the dog's breed? I noticed in Show Bostons, they too have pure white bellys and chest. Not that I'm concerned whether or not Smudge is "breed quality" but I'm curious. My little speckled hogglette.