I have stayed at both. Here are my thoughts:
1. BED CONFIGURATIONS-
AoA: Has a Queen bed in the bedroom and two double beds in the living room area (the sofa bed and a the dining room murphy bed).
ASMu: Has a Queen bed in the bedroom, a double bed (sofa bed) and two twin beds (the ottoman and the chair both convert to twin beds).
We are planning a trip in May and this was a critical factor for us in picking ASMu since there will be 5 adults (including two teenage boys) and one 5 year old. An adult and a child can share the AoA double beds easily but the double bed in AoA will be too tight for the two teenage boys to share comfortably. In ASMu they will each have their own beds, so much easier. I don't know if this is a factor for you.
2. AMENITIES -
AoA: The pool is great and much better than any All Star or Pop. The food court was ok in our opinion. Yes they do serve a wide variety of non-traditional foods but only one item we had was really excellent.
ASMu: The pool is fine and the food court is the same as the other ones at the All Stars.
I'd give the nod here to AoA because of the pool area.
3. BATHROOMS -
AoA: two bathrooms but one is inside the bedroom. The bathroom in the master bedroom does not have a tub but the shower was really nice.
ASMu: two bathrooms both outside the bedroom (one is off the kitchenette area and the second is off the living room)
Having a bathroom in the bedroom is good and bad. For us (we were only 4 when we stayed at AoA) it was nice but with a bigger group it may be easier to have full access to both bathrooms for the entire group as opposed to 2 people using the master bathroom and 4 using the second one.
4. THEMING -
AoA: both the resort and the suites are themed to the MAX. It is also still all very fresh and new.
ASMu: themeing is mainly in the resort as the rooms are not very themed. It is also a much older resort in comparison to AoA so it has some expected signs of aging.
AoA is a gorgeous but VERY VERY over the top resort. Kids will LOVE the themeing at AoA.
5. BUS TRANSPORTATION - we did not use but AoA has a dedicated bus while ASMu shares with the other All Star Resorts at times.
Overall, I am glad we stayed at AoA to try it but I would probably stick with ASMu in the future for the better price.