Tough poll...

They are kind of even in both look and skill. my fav started with Rina for that beautiful smile, then Mami for her guitar skill, but later realized Haruna's eyes and voice were pretty hot. Then came Tomomi with her funny character and pretty face. I mean, picking one is like picking a favourite Beatle, which is impossible.
I think I quit my interest for childish/ girlie J-Pop (namely Momusu) for along time, but these girls brought me back with a bang (not Momusu anymore though). SCANDAL is a refreshing wind in the nowaday J-Pop world that are saturated with similar, generic material. The fact that they participate in writing their music's lyric is pretty amazing given their young ages.
I dropped a vote for Tomomi. If I have a chance to meet them, she's probably the one I'd like to hang out with the most. It's scandalous to say no to a megacutie like Rina, but the goofy side of Tomomi is very interresting to me. She also has beautiful, long, straight hair (I don't count the hairdo for "Pride").