Having grown up reading authors who played with language to achieve incredibly powerful and evocative prose, I'm loathe to limit myself at all. If I'm going to write a Regency bedroom hopping farce, I might use "quim." If I'm writing something set in the 1970's, when we all strove to shock, I'd use "cunt." If I'm writing a scholarly piece on the experiences during a vaginal birth after caesaerian, I'll go with vagina and cervix. It's all mood and the music of the words.