I've stayed at both, and they wife and I love AKL much more so than the Polynesian.
Everyone can go back and forth over the little things like sq. footage, the monorail line, etc. But for us, it's all about the theming of AKL and the animals.
We loved our stay at the Polynesian, don't get me wrong, and if AKL was not a choice we'd probebly end up at Polynesian or the Wilderness Lodge, but we just feel AKL is the best resort.
Here's our resons why:
The animals, the staff, the conceiage lounge and service, the food - BOMA and JIKO, Sunrise Safari tour (need conceiage for this), the resort itself.
The last one is in reference to all the art and history placed around the resort. They even have tours of the resort by CMs.
When we stayed at the Polynesian, it ended up just being a nice place to sleep at night. We never returned to the resort until the parks closed, and left first thing in the moring. After the initial walk around the first night their, it was just a nice resort to us.
But at AKL, we found ourselves lingering around in the morning, not in a rush to get to the parks, we would watch the animals, have a nice breakfast at Boma, talk to the African CMs, which btw everyone should do. These CMs are great to talk to, they have a welth of information and stories to tell. And we would return the resort in the afternoons, and evenings more often than not.
It just felt more like a vacation resort than the Polynesian did for us.
Have fun in either resort you stay at!