There are three character meals with the princesses:
Cinderellas Royal Table in the castle - PS's are hard to get, have to call early that morning of your 90 days out. This is the only one Cindy is at (breakfast), and there *is* something about eating in the castle... I'm not sure it's worth all the hype and anxiety that PS obtaining seems to get but... *shrugs*
Princess Storybook Breakfast at Norway in Epcot - various princesses are at this one, with exception of Cindy. We are doing this one this time around, so I can't attest to it yet! I am looking forward to it! Again, I think PS are always necessary, but not as crucial to get in 90 days like Cindys
Cinderellas Gala Feast (?) at 1900 Park Faire at the Grand Floridian resort - I have had their character breakfast with Mary Poppins, but not the dinner. From my understanding, Cindy, Prince Charming, the mice, and the Fairy Godmother are at this one.
REmember that character breakfasts are not about the food... though I'm sure its nice to have decent food, you're paying for character interaction... I honestly dont remember any of teh food quality at any of the character meals I've had during my years of visiting Disney, I *just* remember the character interaction and how much fun it was to be there with them. Pick the characters that will bring your child the most joy, not necessarily which food is going to be the best... Just my opinion. =)
Good luck in your decision!