I personally prefer the sound of a catted pipe over an off road peice. The catted pipes have a cleaner, less raspy sound, and on a mostly stock vehicle you are gonna lose some low end with the off road pipe. I personally have used a Bassani catted x, and an off road x, and I didnt like either one of them as much as my MRT catted H pipe I am currently running. It gave the car more of the deep musclecar tone I was looking for. As far as gains go, Im not too sure. I think the off road x will give you the most peak HP gains, but i think its gonna be top end power. I chose my exhaust more for the sound anyway because your only gonna gain a few horses that you probably wont even feel, but you gotta live with the sound all the time.