Champion vs Hero

The terms "Hero" and "Champion" are used a lot on Buffy and Angel, and I've been a part of several "Are Angel a hero or not" arguments which can get confusing, so I think this definition of the terms written by Emmie (from slayalive.com) is handy:

"All heroes are champions, but not all champions are heroes.

A champion is a warrior who fights for the cause of others, be the cause good or ill. A hero is a warrior for good.

The terminology is a deliberate choice. As Giles puts it "Buffy is a hero, you see?" while Angel is a champion. Angel is the vampire with a soul who could go either way in the apocalypse. No one knows what side he'll land on, they only know he's pivotal. That's why he's not labeled simply a hero."

Source

It's still up for debate what is a good cause and what is not. I bet Angel would generally define himself a hero as well as a champion, and as much as I loathe some of his less un-heroic choices he didn't seem to feel bad enough about (I mainly thinking of him killing the demon slave in Not Fade Away), I would have to agree with him. Just as I would agree that any demon was a champion if he was working for someone else as a warrior.