Rescues and shelters are different, shelters are usually subjected to keeping up with laws and inspections, some "rescues" are just businesses started by ordinary people. I would trust shelters over rescues. 
Sad part is that "ethical breeders" are few and far between. Most don't even get licensed and go under the radar. It is very, very difficult to find a good breeder. I'm a vet tech and I've seen even AKC registered breeders continue to inbreed and sell puppies that need to be euthanized before 1 year old due to congenital problems.