I would recommend a 12 gauge only because the more shot the more likely a clean kill. I've never found barrel length to be a big deal. I have an 870 Exp. with a shorter barrel, and a Nova with a barrel on the longer side and generally my mood determines which I take more than barrel length. That being said I believe most prefer a shorter barrel, cause it's easier to swing around for a quick running shot without getting snagged. Camo goes the same way. It doesn't really matter to me, but some find it easier to make small movements without being seen using camoed guns. Chokes will probably start a debate. I have a Buck Kicker Full 00 choke in the Nova. It shoots Winchester 00s, Winchester #4 buckshot, and Hevishot 2s and Bs so well I never bother to switch it out no matter what I'm hunting. The Remington is a little more finicky. It shoots Winchester 00s and Federal #4 buckshot great with the factory Mod. tube. With a remington Ex. Full tube it shoots Hevishot 2s and lead 3" 6s the best.

Chokes will be your biggest problem. You're either gonna have to pick the shot you wanna use, and buy chokes till you find one that will shoot it, or pick a particular tube, and buy shot till you find soemthing that will shoot well in it. The latter is generally MUCH cheaper, but you may end up with a shot size that's smaller than your intended game at the ranges you want to shoot them. I just got lucky that the first ones I bought for each gun did exactly what I wanted.