i've had both and concider the 870 a better shotgun. Choke-Tubes are easier to find than for accuchocks that mossberg uses. 870's also throw an accurate slug. Overall, the quality is much better than mossberg. The combos are pretty cheap too. I would get the one with a rifled barrell too.
good shooting!

I'd go with the Remington myself. They make a better gun and the interchangeable barrels are very easy to use. That being said if you can find a deal on a 500, go for it.

i have owned 2 535 and i love them you cannot go wrong with this gun.

I have and 870 in 16 Ga that was manufactured in 1961 ( Verified by calling Remington and giving the Serial Number.) I have yet to have a problem with it. So of course I prefer Remingtons, I have 3 of their Shotguns, and 2 Of their rifles at the moment (Have have more in the past and expect more in the future.) {8^D

The 870 in 20 ga. was my dads first shotgun that he handed down to me. Was a great starter gun! I have never had a problem with it and still use it on upland birds. I am also an owner of a 12 ga. Mossberg 500 Ducks Unlimited Edition. I use this gun for turkey and occasionally grouse. Both are great guns and both serve a purpose in my collection.

also 870 for me

Based upon my own experience, I would get the Remington.