Now, I don't necessarily mean, "Which is your favorite song that hasn't been released as a single." In my opinion, the songs are all good from a musical standpoint. I'm looking at it more from the combination of the musicality and the lyrics. Which song do you think has a message that most easily translates into potential for a great video (assuming they story for the video is related to the lyrics, which is always a big assumption).
(I'll hold my opinion until later. I'm more curious what others think.)