Tony:

Tony likes any types of buns. He thinks you look amazing in both messy buns and high buns.

Steve:

He likes your hair to be loose and wavy. He doesn't quite prefer any specific type of hairdo, but Steve thinks you look amazing in whatever one you wear.

Thor:

Thor loves it when you wear braids. He doesn't care which one you pick, because he simply loves all that you wear!

Clint:

Clint straight-out loves ponytails. He loves the way it sways back and forth as you walk. Clint also thinks you look amazing in ponytails because it keeps the hair out of your face.

Loki:

Loki prefers a pixie cut or even better a faux undercut. He loves it whenever you are wearing a fancy hairdo.

Bruce:

Bruce loves your short hair. Although, it's not like a pixie cut type of short. It's about perhaps shoulder length or even chin length. He just likes it because he likes you look lovely in it, while also it's not so much of a hassle of take care of.