Vets are neuter/spay crazy. They want to neuter the little buggers before they ever developed. All you have to do is look at a steer vs. a bull or a stallion vs. a gelding and you can see that testerone plays a huge role in muscle and attitude.

I just had my GSP netuered at six years of age. I never bred him because while he is a nice dog, he certianly is not a great dog, and there are better breeders out there than I could ever hope to be.

Let him develop, then if you want to neuter later, do it. I would neuter all males somewhere around six or eight years to help avoid prostrate problems later in life and possibly extend their lives.