Breakfast gets a majority of excellent reviews for food and character interaction. Dinner gets a mix of food and character reviews, maybe tilting to the negative side.
We always do both, and probably prefer breakfast (with a first seating PS). Early breakfast doesn't seem as busy and the food quality is better than most of the breakfast buffets (omelet bar). Also, for those that have to have the PF bread pudding or strawberry soup, both are available at both dinner and breakfast.
In case you didn't know, characters are different at each meal. Dinner is Cinderella characters (Cindy, Prince Charming, Suzy, Perla working the room and Fairy Godmother usually out in the lobby). Breakfast is titled storybook or something like that. Every time we've been it seems to be more of an English storybook, with Pooh and one of his buddies (Tigger or Eeyore), Alice, Mad Hatter, and Mary Poppins (with Bert sometimes) out in the lobby.