Dogs and cats sitting in pigeon holes for sale are the worst place to obtain your pets. Proper and ethical breeders would be able to tell you the following : sire & dam, temperament, build, bloodlines, size at maturity, minimal defect (as they are bred for perfection rather than for $$$), MKA certs, microchipped, etc etc. something which any petshop who obtains from BYB can't do.
If you are seriously looking for purebreeds, do your homework and search for a proper breeder. Look at the food they feed, how they exercise their dogs, how they train, how the dogs are housed in kennels etc then compare against the pet shops. Real breeders will not sell to anyone and you will be evaluated on whether you are qualified to take home their puppies. The choice is clear