I would have to say the Alliance -- they fight the good fight and stand up for what is right.
Definately the imperials. I'd love to be an imperal officer- I look good in black and....I would definately do anything Vader asked even kill my own comrades if they were traitors. Blowing up innocent planets, killing rebelscum, murdering treacherous folk=love it! Let's not forget sending stupid Ewoks and other "things" skyhigh with laser blasts...lol..great!
Edit: Okay, I forgot something.. the imperials have THE best theme music too, compared againt the ..sigh, lull you to sleep boring- ass "wannabe hero" music of the rebellion