I was reading recently--don't remember exactly where--that it's thought that ceratopsians with big brow horns (like triceratops) were more likely to butt heads like sheep, or lock their horns like deer do with their antlers, while ceratopsians with much more prominent nasal horns (like centrosaurus) may have been more likely to actually use their horns for defense, like a rhino.
Ceratopsians like achelousaurus may have mostly used their horns and frills for just looking pretty.

that's not entirely related, I suppose. But, you know, horns on the brain...