Who is stronger: Naruto or Luffy?

Who do you think would win in a battle between Luffy from One Piece and Naruto from Naruto?
I would like to know who you think would defeat the other and why. Personally, I think Luffy, but I`m not exactly up to date with Naruto, and also, i`m not sue exactly how much stronger luffy has grown over the time-skip. Chief - Hmm ...
We have a similar topic here where this can be discussed :
http://worldbeyblade.org/Thread-Naruto-S...More-Anime