Your ability to use whatever shotgun you get safely and effectively is far more important than which make/model you choose. Any reliable pumpgun will meet or exceed your needs.
The Remington 870 and the Mossberg 500/590 are still in production, unfortunately the Winchester pump or its FN clones are no longer being made. There are tons of great used pumpguns out there, any number of which are now discontinued as far as current manufacture goes, but for a 'first time out' buyer I would strongly suggest sticking with a gun that is current production, no matter whether you buy new or used.
If you look for used guns and are not already familiar with what to look for and look out for in the used market, find a friend who knows shotguns well to help you - or buy new. That's the best advice I can offer. As to which to start with, handle examples of both manufacturer's products at the gun shops near you, and see if either fits or feels better to you. If possible get family or friends to let you try out their shotguns in live fire on the range (you buy the ammo - start with light birdshot loads) so you will have even more data to help you decide. But make up YOUR mind based on YOUR experience, more than just blindly following advice on the internet.
And for Pete's sake please start out with a plain jane box stock riot gun and learn to run that well first, don't feel as if you have to add on a bunch of pistol grips, folding stocks, magazine extensions and other tacticool stuff before you even shoot the thing the first time. YOU are the only tactical thing in the equation, YOUR mindset and skillset matters FAR more than whatever hardware you buy.
Among the pumpguns here are Remingtons (870s are my favorites overall), Mossbergs, Winchesters, Savage/Stevens, Ithacas, High Standards, one Browning pump and CCCs (cheap chinese clones). The latest pump shotgun I bought (just last week) was an old used High Standard Flite King clone with Sears Model 20 markings ($145 OTD, in great shape), so I'm not choosy when it comes to a good deal. I do have favorites and I admitted that up front, but because I like something doesn't mean you have to.
Good luck shopping, and Stay Safe,
Mindset - Skillset - Toolset. In that order!
Attitude and skill will get you through times of no gear, better than gear will get you through times of no attitude and no skill.
Last edited by Lee Lapin; June 13, 2011 at 08:47 AM.