If he's not ever going to have a bunny companion and doesn't show any unwanted hormonal behaviors(spraying, mounting, etc) that are causing problems, then I personally wouldn't neuter, especially if he is pretty docile and not very hormonal in the first place. I had one of my boy buns neutered and he was a pretty calm boy before. Now he doesn't seem as happy and loving as he used to be. Almost too docile now. But I did it so he could be with the rest of his bunny family. But if he was going to have been a single bun, I never would have done it. And I almost wish I hadn't now, I miss my loving boy.
As for the risk of testicular cancer, sure it can happen, but it's pretty rare. Plus as safe as neuter surgery is, there are always risks with any surgery. So no reason to take the chance if there is really no need to, but that's just how I feel about it.