The Serpa is both. It's not uncommon for the mechanism to fail and lock the pistol in the holster. Plus the finger release method problems in general.
I usually run a few boxes of light target loads, a handful or 10ish of heavier shot (turkey loads or 00), and a handful of slugs. Another way to vet is using hunting. If the shot doesn't break it's not the end of the world, but you can get excited and the gun needs to be reliable. If you do a decent amount of shooting and a hunt or two then I'd be comfortable enough for my personal defensive needs.