Unless your dog is an extraordinary specimen of the breed and you are willing to health test and show and some day breed to extraordinary females who have also been thoroughly health tested you should most definitely NEUTER your dog.
Your pet will have a much healthier, happier life if he is neutered. Neutered dogs have fewer health problems (re: repo tract health) and fewer behavior problems (including not wandering in search of females or male-male aggression). I think every pet owner owes it to their dog to make a responsible decision and alter their animals. Breeding should be left up to the people that know what they are doing to better the breed.
I have 2 males that are neutered. I noticed a lot of improvement in the overall temperment of my terrier after neutering.
Good luck in your decision making,
Tam