To the best of my knowledge the x pipe may give a bit more top end, but the h sounds better and is good at low and high rpm's. The difference power wise I doubt you would feel. I think it is mainly the sound, but like I said the X is supposed to be a little better performance wise. Most prefer the sound of the H pipe. People with X pipes may have different opinions. I have a MAC catted H, sounds great, I never heard an X in person.