In a semi auto if you get a fail to fire you have to come out of your mount to cycle the action, if it happens in a pump you can just pump again. Pump shotguns are the revolvers of the shotgun world, if something goes wrong it is a simple fast process to get another round in the chamber and ready to go. Also auto loaders can have issues with failure to feed if you are using bird shot or any reduced recoil round, with a pump there is no issue.
I think it looks like a great shotgun, 18.5" barrel which means with slugs you are accurate out to 100y. Switchable mag tubes so you could have one full of slugs and one full of buckshot, if you need a slug just switch and pump.
Keltec makes great products and stands behind their guns with a lifetime warranty, also it's made in America. I have a P-11 and love it.