All dogs should be neutered or spayed unless you intend to breed them and there are too many breeding issues to go into here. Neutering helps the animal, and you, in many ways! Possibly the most important is that it eliminates the worry of testicular cancer and other illnesses.
My husband didn't want to neuter Hammer at first because, like many, he believed that it would change his behaviour or stunt his growth. It did neither! Hammer is still the same boy he was, and he's growing like a weed still!
Good luck, you're sure to get lots of responses here about this topic. You could also try doing a board search on neutering for more information.