Our family had great experiences at both places, but Chef Mickey's was more memorable. The characters were great. We had an early dinner and found the food to be good. We are definitely going back.
We loved the Akershus breakfast as well. The princesses were sweet, but their interactions were much more brief. The food was good, and the (free) picture with Belle was an added bonus. That would be a nice keepsake for the 16 of you. I think you get one picture for each group of 4, so you would have 4 pictures I think. (Not sure if I am completely correct on that one - maybe someone could confirm???).
If I had to choose for my family, I would pick Chef Mickey's, but I wouldn't hesitate to go to Akershus again either. Although I will say that the lunch or dinner menu interest me there. However, with 16 people, that is a lot of ups and downs to the CM buffet, whereas Akershus is also part sit down which might be nice for your large party.
Good luck deciding.