On girls I prefer long hair without bangs, or at least not very heavy bangs. I don't know why I don't like bangs I just get the feeling that they look lobotomized, I can't explain it really xD Different lengths and layers are also a good thing.

On myself I prefer very short, like this. I'd love it if I could pull off the long hair look, but I just don't think my head is big enough for it, I end up looking like I'm a kid. Plus, my hair isn't very thick so it'd get long and straight, not big and wavy.

On other guys I think they suit short hair better, I often think it makes them look more manly and adult after a haircut. This can go both ways though, some guys really suit the long haired look.