ThingKing
Child in Time
The 2 inch is a fair bit quieter than the 2-1/4 and only gives up 4 to 5 hp and they both produce similar torque numbers. Unless you have to win the horsepower wank competition I'd go with the 2 inch. If I was getting a new pipe I'd get the 2 inch again.
My hp wank competition is only including my Roadster and my old and sold Hayabusa. Should be rather easy, it was 152 hp stock.