I'm left assuming the OP is asking about the Rem 870 and the Mossberg
500- 12 gauge pumps.
Rem 870s are a little heavier, a little better quality, but cost
a little more.(@400$, for the basic gun)
For that much, I got my Mossberg 500, NIB, with an 18" and a 28" barrel,
and three chokes for the hunting barrel.
Ithaca, and others, also make a fine 12 Gauge pump.
For price comparisons, use Bud's Guns, J&G sales, and Gunbroker.
Remember to add shipping(@35$)
Insurance, and your FFL costs(@35 to 50 $) plus any other applicable taxes and
fees to the cost of your "Oh, it's only xxx.xx at Bud's!" gun.