In my experiences, I've found that the un-neutered dogs at the dog park are always the ones humping other dogs, playing more dominantly-aggressively, marking ON other dogs heads and marking everything around, and just more hyper in general. I am all for neutering male dogs and do think that most of the time it makes for a better pet. I would never own an un-neutered male dog. An unaltered male will spend his whole life searching for a female in heat. Naturally, they want to mate two times a year, when females go in heat. If they are not able to fulfill that "desire" if you will, it can make them crazy. They're also more prone to wander to search for that female in heat which they can smell miles away. However; I understand your reasoning NOT to and respect that everyone has their own ideas, and nobody knows their pets better than you so you will know what's best for your dog.
Kinda O/T but in my personal opinion, I think it's dumb that altered dogs can't be shown. Any dog can compete in agility, I'm pretty sure.