Neutered males are much more prone to weight gain, that's the biggest con to me. Mine calmed down more than I prefer, I would like to see him more enthusiastic than he is sometimes.
Not neutering your dog will not magically result in more puppies, assuming you keep your dog properly contained and communicate with other dog owners to make sure their dog he is coming in contact with is not in heat. I assume you've done well at this so far.
I prefer keeping dogs intact, I don't buy into the whole 'it reduced risk of cancer' when vets say it. Why not cut off tails, ears, noses, legs, remove all teeth etc so they don't get cancer in those body parts? Some medical websites also say it increases the risk of other cancers due to less testosterone in the body.
Pros: Won't chase after females as much
, less competitive, male to male interaction will go smoother, can't get a female pregnant if that's a concern.
Cons: Risks obesity (can be solved if you keep an eye on weight), can become lazy, less enthused, and risk of incontinence is increased and for younger dogs it can poorly effect maturity.
There are plenty of insightful websites if you google "pros and cons of neutering".
Here is Dr. Karen Becker's opinion on it: Why I've Had a Change of Heart About Neutering Pets