I don't really have any contribution to make in answering the question but I am just curious what you mean by "small girl" and "big girl". You say you don't mean thin or fat you are talking about the size of the body, but size of the body partly means thin or fat doesn't it? Do you mean just height then? If you're talking about height I think most people of both sexes would say the guy should be taller but it's a factor you can overlook if you really like each other anyway. If you are talking about thin/fat there are a bunch of variations it's not that simple :)