Do you spend a lot of time in your room?
We LOVED the WL resort -- the lobby, the restaurants, the atmosphere, the "secret" little nooks, the peacefulness of the setting. And in the holiday season, it's really in its glory. BUT...the rooms were small (IMO) and pretty dated looking. We tend to spend a lot of time in our room, so that was a killer for us.
The Poly, on the other hand, has nice spacious rooms that are great for lounging in. We never felt cramped. And it's of course super-convenient with the monorail & being able to walk to TTC. We just weren't that wowed with the rest of the resort, plus it's not the best for holiday decor (if that's your thing).
So if you're basically in your room just to sleep & shower, I'd go with WL. If you spend a lot of time in your room, I'd choose Poly.