La Nouba was the first CdS show I ever saw, so it was jaw-dropping, wide-eye amazing. Since that time, I've seen O, Mystere, Varekai, La Nouba (again), Drallion, Zumanity, and Ka.
O is "bigger" than La Nouba, but I think that the variety of acts in La Nouba puts it at the top of my list. All of the shows are incredible and worth the cost of admission and travel.