I noticed a significant sound difference. I did a sound test (just my ears, no recording) in my garage (door open) before and after and there was a very noticeable change in the sound and DB. Not Loud, but certainly louder. It reverberated in the garage more than stock, and allowed me to hear the low end more, big smiles. Also, riding it with the same helmet, I could hear the bike more than before the xpipe. It def gave it more of a rumble, and better throttle response. Was it a huge change, absolutely not, a worthwhile change, for me, absolutely and would recommend it.
I am not sure of the merit behind it, but there have been some articles and videos from xpipe engineers (xpipes for the Bobber, Bonneville, etc) stating that where the xpipes are cut and welded (creating the connection/gap between left and right side of the pipes) is crucial in the xpipe being functional as a performance mod or simply getting read of the weight of the catalytic converter.
There are other folk that have done slip ons, and then the Xpipe after the new pipes, and have stated that it made even louder/deeper. (BC shotguns w/ xpipe are apparently really loud, whereas BC Shotguns with NO xpipe are not so much (still loud, but not car alarm detonating loud).