Based on my experience, the only reason I would get a boy bun neutered is if I planned on bonding him with another rabbit or he is an indoor rabbit displaying excessive hormonal behavior(spraying, humping, marking, aggression, etc). If he was a well behaved happy boy and I had no plans on bonding him, then I probably wouldn't risk a neuter. But this is just me offering an opinion for an owner with only one boy bun and no plans on getting another. I myself have 10 rabbits, and all are spayed and neutered.
Most of my current boy buns were very friendly, affectionate, happy boys before being neutered, then after their neuter they are more subdued and not quite as spunky and friendly. I just had my last boy bun neutered. He was just the sweetest little guy, and now he is still a very sweet boy, but not as interested and affectionate as he used to be with me. But saying that, I still would have had him neutered even had I known that beforehand, as he was on his own and I wanted him to be able to be with his bunny family. He is now bonded with his mom and siblings, and I am very happy to see him be able to snuggle up with them and not be alone anymore, but it does also make me feel a bit sad not to see him as spunky and happy as he used to be.
With girl buns, spaying doesn't seem to affect their personality as much as the boys, but this has just been my experience with my rabbits. My boy buns were not excessively hormonal and I didn't have issues with spraying, humping, or aggression, so it might be a different experience if the rabbit is really hormonal. I also know that other people have had positive neuter experiences where it has helped the rabbits personality to not have those hormones causing issues. But there are also those very rare cases of it changing an affectionate rabbit into a grumpy one. You just have to weigh the pros and cons and make the best decision possible. I personally don't worry about the risks of testicular cancer for boy buns as it seems to not be as common an issue as uterine cancer is for girl buns.