Remington 870 EXPRESS
PROS- Receiver is milled from solid steel,Tons of add on's and upgrades available, easily disassembled for cleaning, great combos available for a good price.
CONS- Quality has slipped in the last few years, Rust is a problem, laminated stocks tend to swell when wet, single shell extractor.
Mossberg 500
Pros- Dual shell extractors, Tang safeties, Great combos available, easily disassembled for cleaning, passed US military testing (includes 3000 rounds of 00 buck down the pipe) becoming a standard issue shotgun before the Benelli M4 S90.
CONS- Aluminum receivers (i prefer steel), camo paint flakes off, plastic safety and trigger guard (military spec is metal)
BPS
Pros- Bottom eject for the lefties out there guys beside you in your duck blind will thank you, great walnut stocks with nice bluing on all metals, back bored barrels, tang safeties, Milled steel receiver.
Cons- Little bit more in price but still cheaper than a Wingmaster, weight, ad on's extra barrels are big $$, disassembly for cleaning can be a pain.
I havent shot Benelli Nova's enough to offer opinions on it, the Super Nova seems pretty slick thou amazing how it soaks up the recoil from a 3.5 shell.
I have a few M12 Winchesters that are great, love the slam fire on them (hold the trigger down and pump).
As stated before, these guns (870,500,BPS) if maintained and used properly will out last you, and for the price you don't have to worry about dog scratches, dinging it of rocks, rain, and all the other crap you put it through.
Thats my 2 cents