870 Express is a smoother, simpler, rock-solid shotgun.
3" shells will do anything you want to do, now that steel is not the only non-toxic option. A 3" pump gun WILL do anything. 3.5" is a waste of money, complexity, and weight.
I'd get the wood stock, personally. The new one is a nice laminate, and I don't much care for plastic on my face. Some nylons and textured fiberglass are fine, but you would need to buy those aftermarket anyway. For the same price, the laminated wood stock 870 Express is a better deal, IMO. You can buy synthetic take-offs really cheap on eBay, or you can buy better synthetic stocks aftermarket if you want one (wide variety of camo, Hogue overmolded, etc.)