I have been to AKL and POLY but not WL. I prefer AKL for the theming and the extra service that I observed between the two. The poly is a good choice if you want to be on the monorail, though. And the pool there is a bit cooler than AKL.
The concierge service at the AKL is the best that I have experienced. They meet you at the front and whisk you past check in, your itinerary is pre printed, they have the concierge guest sunrise safari (at an additional cost, but well worth it) and now offer a sunset safari with a dinner a JIKO included.(also at additional cost...we are trying this one in October) The food is wonderful and quite extensive at cocktail hour and the breakfasts are wonderful too (continental with fruit, smoothies, etc). Wine and desserts in the evening. For us, we received much more personal service at AKL than at the POLY, with pre planning phone calls and emails. I know POLY offers this but I did not get it.
EIther way you will have a wonderful time.