Having been at Poly/AKL/WL each twice--my heart still belongs to Poly. Love the convenience to the monorail and MK (we spend most of our time there). And the theming--what can I say.
As far as AKL, we enjoyed our first trip there in May '02. We split our stay in May '03 between Poly/AKL and we were very disappointed with AKL even though we really enjoyed our first experience there. The biggest problem for my family--the long bus ride to the parks. It seemed like the time spent sitting on a bus could have been better spent in the parks. If it wasn't for that, I would stay there again in a heartbeat.
One hint if you are thinking about splitting your stay. They will move your luggage for you upon check out to the new resort. However and this is a big one--your luggage may "not" arrive until late in the day. We never rec'd. our luggage until after 5:00 in the evening and we had hoped to enjoy the pool that afternoon after spending the morning at the parks. Unfortunately, our bathing suits, etc. were in our suitcases and I would not wanted to have to drag that around the parks to avoid this.
WL is awesome. We really enjoyed it there and would love to stay there again someday soon.