Long or short hair on girls works. I think I prefer long hair in general, but it depends on what suits them. My girlfriend's had both and she looks great either way.

In my case, I like my hair medium length. I would never go for a short style. It makes me feel naked. And I like having hair to style, even though I'm often too lazy to do so on a day-to-day basis. Right now I'm rockin' a long-ish swept fringe that comes past my eyes with a short-ish, but layered back.