I'll be the first to admit that I'm not a shotgun guy, but I've owned a few from Saiga 12 that I had SBS to 870 Wingmaster and currently Mossberg 590A1.
I like the 590A1 because it doesn't use the cheap plastic parts that are on the 500 series. I also like that my 590A1 has ghost sights.
I like the safety position of the Mossbergs compared to the 870 Wingmaster that I owned. If you put a pistol grip, than the 870s will have the safety location advantage. Mossbergs feel strange with pistol grip to manipulate the safety.
If you get a 12 ga...take a look at Federal with Flight Control...I believe it's LE00132...that line of shotgun ammo produces the tightest pattern I've ever seen on a shotgun for home defense.