Kinda interesting question. What is it that you really want to find out? I take it as when you are going to meet a girl and you're going to score in having sex with her thus probably you would want to last longer? or is that you want to be less anxious like in the movie 'something about mary'?
Well honestly for me, if you have issues of premature, then you should jerk off first, if it helps to make you last somewhat longer, that's if you are going to have sex with her the first time.
But if you want to jerk off everytime before you meet girls then there could be some sexual issues present. Imagine if you are going out for a drink or lunch with girls and you decide to jerk off first to ensure you are not so anxious or have funny ideas when you see them?
Anyway I'm just commenting, and I don't really have an answer to your question.