I think just about everyone has owned at least one 870. They're great shotguns. The supernova will be the toughest of the bunch. It's a throw it in the mud, shoot, then wipe it off if you feel like it kind of gun. It's also much more clunky and rattle prone than the other two. I personally hate the location of the safety on the supernova, but other than that I love the gun. I can't say I've ever owned a BPS, but I've heard nothing but good about them. Sounds like you can't go wrong with any of them.
Get a 28" model, then find an 18" barrel on the net for whatever brand you decide on. Prices aren't that bad if you do your homework.