For myself (a girl) I prefer middle length. (below the chin- shoulder length) I'm short and really long hair looks awkward on me, and it's too much upkeep. I can't do Short hair either, I have wavy hair and it would just cowlick all over and I'd have to use loads of hair product to make it look good which I don't wanna do.
On a guy I don't care. They can wear their hair any length and it's fine.