The interaction at the Fantasy Faire is fun if you're just looking to meet the princesses. I don't think it's much different from the character meal except that you get them all at the meal and you only get 3 for at the fantasy faire. Like bumbershoot said, you have very little control over who's there, although a CM told me that Cinderella, Snow White, and Aurora usually do the last meet and greet of the day at PFF since they're "Walt's Princesses".
I'm an adult and have had fun interactions with them. Snow White asked me my name and called me Prince. When I met Aurora, I bowed before her and she curtsied back(just like she does in the film when she sees her parents after Phillip wakes her up). She then called me Prince and asked me to take her hand and drop to one knee for the picture.
I've also had nice interaction when I met Aurora near the Hyperion in DCA last June. The character meal option offers the fun of having a meal with the princesses, but if you just want to see princesses and don't really care who you meet, the fantasy faire is a less expensive way for you to do it.