I'd say go with whatever you think suits your character's ,well, character the best, whether it be Tweener, Face, or Heel. You might also want to consider how your roleplays will be affected in terms of quality. I've done all three, Face, Heel, AND Tweener just while I was in R&RW. But, what I noticed yesterday while I was looking back on all three types of RPs that I did over there was that when I did Heel RPs, the dark side of my personality came out a lot, while when I did Face RPs, my nice side came out a lot, and my Tweener RPs were based off of my normal personality. That being said, my own personality was affected in a small, but sufficient enough, way by how I was writing the roleplays, whether Face, Heel, or Tweener. I've also seen other people who tend to base their character's personality off of one aspect of their own. Sometimes it works out and results in a great character and great roleplays, but most of the time, it results in a character that just won't work for any fueds or storylines and is basically a flop (I think you know what I mean, even though I can't find the right way to say it). Keep that in mind, and do what you think will have the best results for you as a person and your character in this federation.
Sorry for the length, just needed to get my point across.