if you look at dynos between the two, the HFC and the ORP are right about the same, its just a matter of where you see the power. IIRC, the ORP will give you gains on the high end and the cat will give you more power in the middle.
IMO you will be better off with the cat, have a better chance at passing emissions (PM sent about that), and it will sound WAY better. I have hear clips of ORPs on stock focus exhausts and its not that impressive. I have a cat on mine now and it sounds nice...a lil louder, but just about the same tone.
..:: sleestak ::..
"Our mother of blessed accelleration, dont fail us now!" -- Elwood Blues