They are so different in feel its hard to compare. I have not stayed at AKL but having been there to eat, it seems like one of the more immersive themed Disney resorts. It has the animals and the African theme and its pretty spectacular inside the lobby and outside.
AKL is a more typical hotel set up. There is a central lobby to walk into, it has things like interior corridors, room service and just that hotel feel.
OKW is more of a condo type resort. Multiple buildings, exterior hallways and no room service (they do have bell services that can help with your luggage and a guest services that can help you with getting tickets, to other Orlando areas etc.). It has the boat to DTD and that is very nice for dining and shopping. You can park right outside your door if you have a car which is great and the bus system has always been good for us. Its spread out but we like that.
Now if you are comparing Animal Kingdom Villas to Old Key West Villas, AKV units will be newer with the granite counter tops and many of the one bedrooms will have the two bathrooms vs. the one bathroom in OKW one bedrooms. The newer DVC units at AKV, BLT and the Villas at GCH in
Disneyland are set up differently as far as one bedrooms vs all the other DVC's. An OKW one or two bedroom is huge, the biggest of any DVC one or two bedroom. The studios have the two beds which is nice for families of four but for a couple, I think a studio with one bed and a sofa is nice.
Some of the OKW units have been rennovated and they look very nice. The older style that many units still have is nice and bright, some of them however are a bit worn.
AKL also has a lot of human traffic in the lobby and around the savanah viewing area. It has popular restaurants that many people not staying at AKL or AKV come to dine at and its a big draw as an attraction in and of itself for people to come visit and look around. I find that lobby a lot like the monorail resort lobbies in that they are always bustling and full of people. OKW's restaurants are pretty much frequented by the people staying there. Its very laid back and a wonderful resort. We love OKW and love that set up of multiple buildings in a spread out layout vs. the hotel feel of AKV or other DVC resorts (except SSR which is set up like OKW).
AKL/AKV rooms will be darker to go with the theme, OKW units are bright and light and very beachy. Being from Colorado, the beach feel, even a fake one, is a big plus to me!