To be honest, the real question is this.
Do you want Cinderella and characters from the movie in a convention hotel ball room or Mickey and the gang on the concourse?
I'd say they're both about the same food wise over. Some days one is more deluxe, some days the other. Some days one is better, some days the other. Some days one is cleaner, sometimes the other. Each has its fans and detractors. The menu's at each for the dinners change fairly often. So the menu you see now might not be the one they have when you're there.
What I would personally do is this. I'd do Chef Mickey's the first night and switch the breakfast you currently have at Chef Mickey's for later in the week over to 1900 PF with Mary Poppins and friends. That way, you're not duplicating Cinderella and you aren't duplicating Chef Mickey's either.
Just pick what characters you'd like to see and go for it is my suggestion.