I voted WL. My DH & I took our 4yr DD and 6yr DNephew last August. We stayed at WL and loved it, here's why:
1. The resort, while a deluxe, is smaller than the Poly and GF. The grounds are not as spread out. When you walk out your room door, you're inside the hotel and don't have to go outside to get to the major hotel areas (Whispering Canyon, Mercantile, Roaring Forks - snack bar, refillable mugs.) With walking all around the parks and such, the kiddo's were tired and we didn't need to hear whining if we had to walk somewhere around the hotel. Things were just closer. Including the pool. This proximity feature came in handy for the brief afternoon rains!
2. The transportation to WL wasn't as bad as I expected it to be. They have boats that run to MK and CR, which are great rides in themselves. Very relaxing and fun to watch all those out on their mouseboats! Made Chef Mickeys and easy character breakfast to get to also. The bus depot wasn't a far walk from the lobby either. Only drawback was sharing some busses with FW and even GF/Poly on an occassion.
3. The kids loved the bunk beds (and I'm sure they would rate this the #1 reason to stay at WL).
I believe WL is also the cheapest of the resorts you listed (which may factor in for some). Whispering Canyon was tons of fun, the storytime in the lobby was something the kids wanted to do, but we never made it back in time. You also have easy access (walking or boat ride) to Fort Wilderness for the activities there for kids (marshmallow roast & movie with chip n dale, petting zoo, hoop dee doo review, etc.).
Hope I helped with at least a little info.
Colette