I like the factory air. I get a solid warranty. It comes with its own compressor. I have a switch on the dash to put it in standard height mode. The back is raised slightly from the front. Or I hit the switch and put in alt mode. This lowers the back of the truck so it is perfectly level. I run in this mode all the time, loaded or not.
When I load the camper or 5th wheel the truck squats a bit and then the air bags kick on to bring it up to level. They don't go off of pressure but have height indicaters to know when to shut off compressor.
I'm sure this is a simplified explanation but I love them.
I have had firestones on 2 previous trucks and they were OK. This setup just feels better and stronger.