I would personally rule out SS right off the bat. I haven't stayed there so I while I have nothing negative to say about it, the transportation options to the parks are just not ideal for me. If you're planning on spending a lot of time at DS, though, it might be more appealing to you. But for me, SS is not exactly comparable to the others.
Choosing between BW and Poly is a tougher call, but under current circumstances I would choose BW, *particularly* if you can get a boardwalk-view room (actually, I DID choose BW when adding a night to our upcoming stay! I LOVE that view), because the current construction at Poly is pretty heavy. There is also construction at BW, but I don't think it's quite as much. I love the ability to walk to two parks from Boardwalk, plus you have the boat and skyliner, and there are just so many convenient dining options when you stay on Crescent Lake. So easy to eat anywhere at Boardwalk/Yacht/Beach Club, Swan/Dolphin, or to pop into Epcot for a meal.