I don't think a kayak is a good choice for duck hunting. Storage for decoys being the first problem and stability another. My guess is from the kayaks you mentioned that price is a consideration. I have fished out of kayaks for over 30 years now and none of mine other than the first a Folbot 2 person would have been a good duck boat. The problem with a good kayak for hunting out of is weight and cost. Weight because stable kayaks are wide and typically heavy. The Folbot weighed close to a hundred pounds but of course that was pretty primitive materials and now they cost over a thousand dollars anyway.
I fish out of a Sun Dolphin Aruba 8' now because I'm old and weak and it weighs nothing but it is also cheaply made, unstable and hard to paddle. Keep in mind because of hull speed the longer a kayak is the easier it is to paddle. I have added pontoons and a trolling motor bringing the total cost to something like $600 dollars but the whole thing still fits in my van and easily hangs on the wall of my garage. Easy storage and transport were my primary objectives. That could be an option for you as the pontoons could be used with a net or something to store decoys etc. Then again $600 is a good bit of money that could go towards a real duck boat.