The first guy I had sex with shaved his balls because he felt it was nicer to lick them if they were shaved. He used an electric razor for that.
Seamus used to do it but he said what he likes is the feel of skin against skin. Since I don't shave anything he can't get that feel so he's not doing it anymore.
Although he's talking about shaving his balls too now so that I don't have to stop and take hairs out of his mouth. I told him as far as I'm concerned, trimming is fine, he certainly doesn't have to shave anything, although he can of course. Having experienced both, I certainly prefer with the hairs, but he's letting me do it my way so I want him to feel free to do it his way too.