I have a 870 Wingmaster in 20ga., and just bought an 870 Express Youth/laminate 20ga. for my daughter. I took the Express out for a test shoot last weekend (about 20 shells) and it ran like a top, INCLUDING the cheap-o Winchester white box target loads. I inspected the chamber when I tore it down for a complete clean before using it~and it was SUPER smooth, no polishing req. I mention this because lots of people complain about rough machining causing the empties on cheap loads to stick~not a problem with mine. Makes me wonder about about the internet hype about how crappy 870 Express guns are. I think it's a function of how many there are out there. Like the study I heard about what dogs bite the most. If I remember right, the answer was "labs". Not because they're an aggressive dog...it's a question of odds-so many out there!
To your question~Wingmasters ARE worth the extra money, but both will go "boom" reliably. Expresses require a little more TLC, but if you take even 1/2 decent care of your guns...it'll likely last forever. When I'm grouse hunting, I see more Expresses out there, and on ATV gun racks, than any other shotgun. They are popular for a reason, not simply the low price. (in my opinion)
Browning BPS~lovely guns, but read-up on stripping them down for cleaning. If memory serves, Browning recommends owners do NOT attempt to disassemble a BPS. Not simple like an 870. I wanted to like them, almost bought one in 20ga, but find they just don't come to the shoulder and point like a Remington does. Everyone is different though.
Camo~great if your're duck hunting, I find the camo a little distracting though. Don't let anyone tell you have to have it...countless ducks have fallen to walnut stocked, blued-barrel shotguns. Probably millions. Yes, manufacturers ding consumers for the camo dip, be it on shotguns, ATVS...whatever.
3-1/2"~I have zero desire to shoot a 3-1/2" shell from a 12ga. I'm not overly recoil-shy, but that sounds like an entirely unpleasant experience. If you're hell bent to shoot the long shells, I'd urge you to consider a semi. A friend of mine just bought a Browning Maxus and says it's the softest-shooting 12 he's ever used.