Interesting topic. I've been pondering this before, but reading all the other's answers, I have to agree that it depends on the context, setting, time, character etc. When I am writing myself, I tend to use the flowery terms, I guess. I don't have any problem with reading the vulgar terms, if it fits the story, and sometimes the more clinical terms can fit as well, as was said before. But I myself tend to avoid both. I am just sure of one thing: "birth channel" will never ever sound erotic for me. Uh. Overdone euphemism can be a major turn off as well, though. It's all in the balance. :3