Neutered rabbits are less territorial, less agressive, don't spray as much, tend to be more affectionate, calmer, and will hold to litter box training better.

However anytime an animal is anesthetised and operated on there is an risk, I don't know why the vet has told you there is a high risk because the risk is minimal under the right care. If the vet you've rang has told you there's a high risk I would be ringing a different vet as it sounds like he might know his own incompetence.