Most people will tell you AKC because they are the "oldest, most recognized and respected registry". (Which is true) I would suggest that you concentrate on the dog and breeder themselves and not so much the piece of paper that comes with them. Just because a dog is of a certain registry, that does not automatically deem them healthy or unhealthy and unethical breeders are everywhere....yes, even with the AKC.
Good luck with your search!