1900 PF is going to give you only one princess for dinner -- i.e., Cinderella. However, it does have Prince Charming, the Fairy Godmother (I think -- she was there when we did it), and the stepmother and stepsisters, too. It is probably our favorite "princess" themed character dining, as the steps are hilarious and really make the experience a lot of fun. At some point during the meal, some ballroom dance type music cranks up and Cinderella and the Prince pick someone to dance with them. When we went, we had two families, including three little girls/cousins all dressed like Cinderella and having just been to the Bippidy Boppidy Boutique that afternoon, and Prince Charming danced with all three of them together. As such, our specific memory of that meal is pretty awesome. Either way, it gives you a princess theme but a totally different type of character interaction (and the only place to visit with Prince Charming if your daughter has any desire to do so).
1900 PF for breakfast will include Alice and Mary Poppins, among other British characters (Mad Hatter and some of the Pooh gang). It is a neat assortment of characters, and MP is one of our daughters' absolute favorites, but not exactly princesses, so just be careful which meal you are planning there so that you'll know what you're getting.
And as a final note, if you do the 1900 dinner...be careful not to put the two Cinderella pictures right next to each other in your autograph/scrap book. On our first trip with our girls, we ended up with three photos with Cinderella from various places around WDW, and as you might imagine, she had woken up on three different sides of the bed during that trip. Thankfully, the girls were young enough (oldest was five) that the issue never came up, but again, we focused on not having the three pix anywhere near each other - ha!