Firefight was ODST. Reach's sucked.
Reach's MP sucked. The campaign was a good story. ODST had an amazing campaign, maybe the best.
I didnt like ODST's firefight mode because you had to build a team to play. In Reach I could just join a random. I loved Reach's campaign. Hell, I loved the campaign in all of these. It's just PVP I don't like outside of Blood Gulch CTF.