There is no pro from buying from a store such as Petsmart. So I would immediately scratch that off the list.
My advice is either buy from a reputable breeder directly OR if that's not something that you want to do... then buy from your local reputable reptile store. The only pro of buying at a store vs a breeder is you can see the animal in person. But a good breeder will send you all the pics you need and disclose everything about the snake. I think you should go straight to the source (the breeder) for the animal. And when I say breeder, I mean the person who actually bred the snake, not a flipper, who buys snakes wholesale and tries to let people believe he bred them.