IF you are worried about being too loud, then just make sure that you get a longer muffler (18" as opposed to 14"). I have a 14" magnaflow and that thing SCREAMS at people if you get on the gas to pass them.
I've compared the Borla w/ the Magnaflow. My magnaflow is quite a bit louder and raspier than the borla.
I like the sound of the mflow and have gotten compliments on how my exhaust sounds, but it is a little obnoxious.
As said above, the resonator is important as well. I still have the stock one on mine. I'm waiting for a catback to come out.