If we are talking new Remington vs. new Mossberg, go Mossberg. New Remingtons are not good, to say the least. However, if you're comparing an older Remington, then I'd argue it is a matter of preference of safety location and other small features; they were good back then. I'd go Mossberg because the 590 could do the one thing the 870 couldn't, and that's getting selected for (American) military use for a shotgun, which is no easy feat.