Mossy 500 an unbelieveable pointer...
Haven't owned or fired a Remington, but my overall experience with Remington products is underwhelming.
I've performed shooting feats with my Mossberg 500 that have AMAZED me. The tang safety and slightly enlarged trigger guard of the 500 are advantages. The open bottom receiver of the 500 makes it easy to clear if you shortshuck. I hear an 870 needs a knife or screwdriver if this happens, but maybe 870's can't be jammed.
The Mossy is cheaper. Overall build quality of the 870 seems better.
The 870 has an almost legendary status, but my experience with a Remington 10C and Remington ammo leaves no magic with me.