Hi,
I always thought that they are the same breed of dog but the powderpuff was a bit of a throwback to when the dog had hair. The hairless variety having being bred on through mutations. I heard stories that people used to shave their powderpuffs on the morning of a show to present them as hairless. Knowing nothing of the breed(s) I can well imagine I have swallowed a totally ridiculous story, but that is what I heard! (I take no responsibility for my being an idiot if this proves to be wrong or for my being an undiscovered genius if it is right!)