Aaron I think you have the right idea. It's much more probable you'd get a dog of similar temperament if you buy from the same breeder as opposed to breed out to a female from a different line. She could be a great worker and so can your male but that doesn't guarantee similar offspring, although you could get lucky. Fortunately when it comes to working retrievers there's not as much BS as with dogs who are bred for the show. There is no opinion with working capability as there is when it comes to aesthetics. The dog either does the job or it doesn't.
My question to you was if you take all the edible meat from a chicken, a goose and a duck, all the same weight, which will have the most yield/edible meat?