If you are talking Christmas week (anything including Christmas day and/or New Year's), Poly hands down just for transportation's sake. We stayed at BWV over Christmas 2015 and I'm so glad we did. Traffic is horrific so buses took forever. The boats weren't great either (monorail will be pretty bad, too). But monorail beats buses every time and, from the Poly, you'll have monorail access to two parks! Yes, WL is lovely, but if you want to go to the parks and not simply gawk at your resort's Christmas decorations, I would book whatever resort you can with the most convenient transportation to the parks.