I had the 18" and I thought it was perfect. It's actually a 1/4-priced clone, but same thing. Nice rumble when first started and when idling. Not obtrusive at all in the cabin when cruising and no drone. It had a strong, but smooth roar when on the throttle during acceleration that turned into an aggressive wildcat growl at upper RPMS. It was actually disappointingly tame when I fist got it. But, it quickly "broke in" and was awesome after that. I still have it, just coupled with the 22" version to quiet it down after losing the cats.
I know it's impossible to get a good idea from videos, but I'll throw my comparison ones up just cuz:
Stock with resonator delete:
Resonator delete with AP Xlerator 1259:
Yes- it does sound quieter and more tamer than stock in the video.
Same setup, one year later:
The rest are after the cam, etc. with long tubes and no cats, so they're irrelevant.
I find that these types of mufflers complement the factory sound in note and volume but without trying to change it. Here's a similar muffler that I believe is a 14", on an older 5.3:
Stock:
After muffler and all else stock: