On an unrelated note: Who is your favorite princess and why?
don't have a favorite, Celestia and Luna are just very interesting. Twilight is Twilight regardless of the new princess title, and although i like Cadance i don't find her nearly as intriguing.
both royal sisters are very mysterious. they've been around for ages, defeated Discord initially, had a fall in with each other, but what about before? their knowledge and history would be very interesting to explore. this season is promising for just that, i hope it happens.
out of those two, I can't really place one over the other. both are so similar when it comes to their roles in the show, they need to be a bit more diverse (Luna's episode was a nice change of pace)