I chose WL becuase I think the resort is amazing and relaxing!! Never stayed there but it is a dream of mine!! AKL is awesome - stayed there a few years ago but the location is not great to me. SO far out from everything!!
Absolutely, On Site at a Disney Deluxe Resort is going to be awesome.
In my opinion it really comes down to personal preference. Do you prefer seclusion or hustle and bustle? Do you want to feel like you are in another country, or in the country, or in the city? Which park, if any, do you want the easiest access to? There is enough difference between the themes, location, and transportation options for each that between the two of you somebody might have a preference that sways it one way or another.
The best part is like you said, you really can't go wrong.
Jellyrolls (where the dueling pianos are: http://www.jellyrolls.us/ ) is awesome! I stayed at the dolphin years ago and it was great being able to walk back from there. BWI would be even in closer.