We have been to both. It is hard to compare them. My husband enjoyed his Reuben and I had the turkey club. We all added the salad to our meal and the ice cream was great. I like having to be able to sit down and have a meal without getting up and down for my food and the kids.
My son like Crystal Palace better, not for the characters, but for the buffet. He liked having more selections.
As for the value of being on the dining plan, I think it does compare when your party is adults.
Crystal Palace breakfast is $18.99 per adult, lunch is $20.99 and dinner is $28.99. For kids it is 10.99, 11.99 or 13.99.
My meal, a turkey club with salad, soda, sundae comes to $23.26, according to the menu listed on Allears. We ate there for lunch.
The Plaza kids meal is $7.59.