Since you throw the word "waterfowl" in, an O/U probably isn't ideal - though I've stopped carrying anything but my O/U for pheasants and grouse.

I'm not a big fan of semi-autos, though. I've not met one yet that wasn't finicky in some shape or form, whether it be ammo, climate, or maybe just the time of day? And, they're not thelightest things, either.Thus, I'd stick withyour currentslide-action.