We all seem to have the same problem helping you because both resorts are wonderful.... We love both for kids...
WL is a winner because you can grab a quick boat ride to the MK and we also like spending time at the Fort next door. We love the Roaring Forks (counter- service). They have a playground at the beach and there is a water pagent at night there on the water). Pool is nice (not as good as AK). Love the atmosphere. It truly is a beautiful resort. Oh and the Whispering Canyon is a great place for a meal.
AK has the animals, that great zero-entry pool, great playground, a really good counter-service at Mara, programs for the kids... Did I say the animals??? My kids went crazy for the animals... they loved looking out our window to see different animals throughout the day and looking out different windows and overlooks on the grounds. We do not like the other sit-down dining choices there (I am sure we are in the minoirty, sorry in advance) because we have simple (picky) eaters in this family... Biggest problem is distance from the parks... We rented a car when we stayed there a few weeks ago because we knew time on buses would be an issue... It still took a while to get to MK. So you have to consider the distance... if you don't mind spending longer trips on the buses (or car) you may really love it at the AK.
This is a hard decision.. One thing you really should figure out is how much time you plan to spend at the MK.... WL is better if you plan on spending most of your time in MK... AK would be fine if you are planning to divide much of your time.