Having said all of the above, if you are up to it, I would actually suggest trying both ACs out (at least until about level 20).
My problem with that is lack of patience (I don't think I enjoy the game enough, but my gf likes it so I am stuck). I am likely to have given up with the class altogether by 20 if I haven't found a style I enjoy, so I am trying to make sure I know what I will like before I get annoyed lol.
Thank you for your answer though. It looks like Pyro is the tree I will look at from the start.