Definitely long hair is more feminine, MUCH more sexy and appealing, in my opinion. The longer the better. If it reaches down to her bajina, then hell ya that's great! Long hair makes a woman. And short hair is manly and lesbian looking -- not nearly as appealing.
Although you've already picked MHO I just wanted to add my two cents ;D I, personally, adore longer hair on men. I do find some short haired guys attractive too, like Chris Pine (LOL). But I've always had a thing for longer hair; anything from shaggy to below shoulders, but they need to keep it clean! I guess I like it because I don't always follow social norms - i. e. I don't dress how society wants girls to dress. I'm a gamer and enjoy rock music over pop. So I must fall in the minority of long hair lovers! ;) It's oddly attractive.
It can go either way, depending on the guy`s overall appearance, hair colour and style. I`ve dated guys of both short and long hair varieties and they each can do awesome things with their hair that they look good with. I have a weakness for spiky haired dudes. ;) While guys with long hair let the whole thing grow out straight is my favorite guy long-hair style and it looks great on some guys.