Oh, and forgot to mention the mechanics of anal! Guys with above average - large cocks (7+ inches) can end up hurting the vagina. When the head pushed against/into the cervix, that can be really painful so they have to be careful. With anal, it doesn't matter how long he is, as long as you start off slow and warm the ass up to get it used to the cock, it goes in perfectly fine! And they can pick up speed and really slam it in without it hurting too much whereas if that happened with vaginal and it hit my cervix hard, I'd have to stop.