Both are great fun, Cinderella's obviously has Cinderella which the other one does not, and is in the castle which is also a treat.
That being said, the aggravation factor in getting the Cinderella breakfast is only worth doing once (it took me five years to get a Cinderella reservation, and we used to live in Florida). The other thing I noticed comparing the two is that at the Epcot (Norway) breakfast the princesses' eyes seem a little less glazed over. Maybe princesses just have to work harder in MK, but they seemed much less rushed and there was much more personal interaction at the Norway breakfast.