I have a thing for outgoing girls...though really I just prefer someone that balances me out. I'm not the most talkative guy, so someone who fills in the awkward silences is someone I prefer to be around. Some people prefer to be with someone similar to themselves, and I think common ground is also important, but I think yin/yang makes for an even better relationship.
Whenever I discuss this question with friends, I think of the Seinfeld episode where Jerry has a mutual breakup with a girl who's identical to him. "I can't date me...I hate me!"
NNID: Zephyr25 / PSN: Zephyr--25 / Switch: SW-4450-3680-7334