well I'll throw my 2 cents in here having had stock, prochamber, mac h, and now an xpipe.
Stock we all know what it sounds like and how it pulls.
Prochamber - lil throaty nice sound not real loud. strong from idle-5500 nice and smooth. WILL not clear a DS loop and allow tech to see it. UGHHH
Mac OR hpipe - sound makes me drool however mine would never stay sealed and exhaust leak free for more than a few days at a time. UGHHH pulled from 2k-5900 was nice felt a lil less torquey down low had to use the gears more.

Xpipe - sound is well an xpipe raspy kinda nascarish to me. kinda weird on the rpm badn though. Pulls good from idle to 2k or so then goes kinda flat till over 4k then rips to redline. So I've found I either have to use the shifter more to either get down into the low rpms for city driving or let her rip to pass on the interstates. very weird IMO. But it is leak free, and clears DS loop.