Not much to say about either, except they both work. It really depends on whether you like a crossbolt safety, or tang safety. Also, whether you like a skinny buttstock grip, or thicker buttstock grip.
Remington 870 = crossbolt safety and skinny grip.
Mossberg 500 = tang safety (ambidextrous) and fat grip.
Maverick 88 is a Mossberg 500 with a crossbolt safety instead of tang safety.
They all shoot well, and would all make a nice HD weapon. It really boils down to which one you shoulder quicker and more comfortably.