Virgin. Just because someone has experience doesn't mean they are comfortable with sex, or even into sex for that matter. So I don't believe there is necessarily anything to learn from a MILF. And at least with the virgin, I know for sure she isn't going to pass a disease onto me, and isn't comparing me to 10 other guys.
But truthfully, it doesn't matter to me much. It's all about the person, not what they have or haven't done sexually.