You get a little less restriction, meaning more HP... The noise from your exhaust will be a little different since all the resonation from your engine will not be gone. You simply go to a muffler shop, cut the resonator off and get them to reweld a straight pipe in between. I f I where you I would remove the cat and the resonator at the same time.. that will give you that much more of an increase and it will cost you a few dollars more.
Jamie