Actually, Maximus had no will to fight after the death of his family. The only reason he chose to fight, well thats open for interpretation. The prospect of revenge wasn't introduced to him until the last act of the movie and his fighting prowess didn't change any. I think whether he is fighting for the glory of Rome, survival or revenge of his family he is going to be the same warrior, like wise for Leonidas. Aggression or any other type of emotion is not going to suddenly give a warrior abilities they never had. If anything it is going to make them sloppy. Aggression and the will to survive may help to cloud pain but in real life, fury doesn't make a person a more skilled fighter.