I'm far from an expert when it comes to suppressors, but to my amateur ear, they sound pretty loud. I also noticed quite a bit of...I believe the term is "back pressure" (excess gas escaping from the chamber/action of the gun) in some of the videos.
From my minimal experience reading the various threads here and watching Youtube vids of other, more established brands like SilencerCo, GemTech, Advanced Armament, etc, I'd go with one of them rather than Coastal.
Of course, I could be way off base. If so, hopefully someone more knowledgeable will come along and chime in.