I love this kinda thread free post
Anyways.
I've had stock hpipe, mac prochamber, mac or hpipe and now a xpipe on my car. So unlike others I know first hand how each felt on the car and how my car sounded with each on it.
stock = well stock and fairly quiet.
Prochamber = liked the deep mellow sound, lots of lowend but doesn't clear and allow inspection of a DS loop

Fit was super never hit it on any bumps.
H pipe = Sound made me feel all warm and funny, was fair down low pulled clearer to the top than the prochamber. Downside was mine fit like POO and I got tired of exhaust leaks. hung WAY too low.
x pipe = lowend not as strong, mid range sound changes to a scream, and it starts to build power pulls cleanly to redline. Others you could feel them falling off earlier than that. Fit is fair, but not as tight as I would like.