Honestly, the decision is ultimately up to you.
I definitely feel that basically any dog, whether they're altered or unaltered, can be an awesome, well-adjusted, obedient dog... with correct training and socialization. That part is up to the owner. I have met plenty of rude unaltered dogs, who hump everything in sight, mark everywhere, and are very hyper; but that's ultimately a training issue, more than anything! My friend's Aussie marked everywhere (including people... watch out! D
before he was neutered, and still does after the snip.
There are cancer risks that you eliminate, by removing a dog's testicles, and by removing the hormones they produce. As people mentioned.
I do feel a lot of it depends on your own responsibility, and living situation. Is you dog ever alone in your backyard? Are there other dogs living in close proximity? If you cannot really, truly guarantee that your boy will never have the opportunity to escape (or the female could come into your yard) and impregnate another dog... then, you should really consider neutering him.