While Mossberg 500 and Remington 870 Express are competitors, I always considered Remington the better product, w/ Mossberg as the "value" play. IMO there is less distinction between them now than in the past, as Remington has slid in quality some.
It's a Chevy vs. Ford thing. I lean towards Remington because it is the one that I have the most trigger time with. The Benelli Nova ia also a good pump. There are no bad choices here.
I've never been a huge fan of Mossberg shotguns but even though the actions are a bit rough and the safety location is less than ideal, I still see it as an upgrade over the 870. I'm not sure there is a more overrated firearm than the 870. The BPS, Nova, and Winchester 1200 and 1300s are all upgrades over both, IMO.
Older 870's are probably a step above the Mossbergs. Especially if you're talking about looks in addition to function. The older Remington's had some decent wood stocks and nice checkering. The Mossbergs have wood, well I've seen comparable wood on a Red Ryder.
Mossberg also makes the Maverick 88. Available in 12 or 20 gauge. Less money and very reliable. Lighter weight and inter-changable barrels with the 500 series. I own a couple of them (one of them sleeps by my bed 24/7) and they have never let me down. Granted, they are not the prettiest girl at the dance, but I am not the homecoming king either. Do wish they had a thumb tang safety though.
Winchester SXP would be in the same price range as a Mossburg- $365 to $375 and the rotating bolt system ejects like an auto all you do is to pump it forward.