First, I want to make it clear that I have strong feelings about backyard breeding. I am very much against it and feel the breeding should be left to the professionals that are truly in it to enhance the breed via hunting ability, conformation and temperament.
With that said, I think that spay or neutering makes a better dog. Of course you need to know what time is the best to do this. And I think it does vary by gender. I have two spayed female Brittanys and they are both great hunters and absolutely wonderful house pets. I'm not up on the proper time to neuter a male but I had my youngest female spayed at 7 months before her first heat cycle. Spaying before the first cycle eliminates some of the possible cancers they might be subject to. They recommend spaying quite early these days but I wouldn't do it before 6 months.
For anyone thinking that spaying or neutering effects a dog's hunting ability, nothing could be farther from the truth.