I don't care much about hair length, but more for presentation. Girls with ponytails, regardless of long or short hair, don't often look that great, because there's nothing to surround or "frame" their face. I also remember images of girls with short hair that I am fond of, like this one girl I knew who had short brown hair that looked almost anime-ish; she always wore off-beat clothing that looked so cool on her, like white stockings with cherries on them while wearing a green skirt. And of course Audrey Tautou in Amelie, she had short black hair that made her look cute, which I think was the purpose of her hair being like that in that movie. When girls have their hair cut very short like a boy, then it still depends how they present it, but I guess that's still a little strange to me. I just remembered this one girl I really like that's Somalian, I think, but she had long black hair that wasn't straight but didn't have those big loopy curls that most girls do on purpose. She usually has it in a ponytail, but that look works for her.
As for boys, I still think it's more for presentation. I guess short hair looks more neat(as in tidy), but if it looks too neat, then it's kinda weird. Like I can't comb my hair and leave it like that, I have to mess it up a bit after. Combing your hair a lot does make it finer though, I guess because you're sort of shaping your hair around on your head or something. I don't like buzzed heads that much either, but some people can look alright like that, I guess. Like Lizard Dude. It's all in presentation. As for guys with longer hair, there's three kinds: afro, limp afro, and lion's mane. People with real afros look alright, because it's a real afro. Then there's the limp afro. Kids with curly hair who have this hairstyle look like that put on a clown wig or something. It just shakes all over and looks frizzy and messy. Of course, I've seen a few of these that look alright. There are also limp afros that are just moderately long straight-haired people, and this looks alright too, excepft when they comb it over their face, so they look like the main character from The Minister's Black Veil. I'm guessing they got a tattoo on their forehead or a black eye or an embarrassing nose, because it looks like they think they're ugly or something and are trying to hide their facial features. Lastly, there's the lion's mane. That's sort of just another way to describe guys with long hair like a girl's. I think as long as they know how to keep it clean, it's fine. I know some guys that don't wash their hair so then they have this long flaky hair that looks like they just came in from a snowstorm. Use head and shoulders, people! Or something anti-dandruff, because believe it or not, it works pretty well and isn't like soy milk or diet cereal where it's obviously different than the regular product.
I guess the real thing to think about it how your hair goes with the rest of your head, or even your clothes. I'm guessing blonde girls don't wear bright yellow, or their hair would look flat or something. And make sure your hair is clean, because that's a bigger blessing to everyone than just making your hair look nice to some people.