I've been with all three before.. (natural chest hair, naturally hairless, and shaves by choice) and I really don't notice a difference. I appreciate both really. Naturally hairless and fresh shaven can be really pleasant (no worries of hairs tickling, or shedding off on you if you're both sweaty, don't smell bad as quickly, etc.) and chest hair has obvious advantages (feels great in your fingers, it's warm, it looks good) and I really can't say I have a preference between the two.
Shaving the body IS a pain in the dick. It just sucks. But there's reasons to do it that are practical. Body hair can get caught on things and be yanked out (band-aids anyone?) and that sucks. It can make you hotter faster, or be a turn-off if you're overly hairy and uncomfortably sweaty a lot as a result. Body hair tends to quickly accumulate odor, so if you're sweaty body hair is going to smell before the rest of you does. It can also slow you down or distract if you're a swimmer or body builder. It sheds everywhere too just like any hair.
I can't say I know many girls that make their dudes shave their chests, but I'm sure it happens. I don't see it any different from dudes expect clean shaven legs and underarms from girls.