POI/POS is more centralized in fewer number of people while POW is centralized via location. Personally I'd rather a few hundred anonymous supernodes spread out all over the world than China having > 50% of POW mining pool control. They are planning to censor even VPN in 2018. Besides, POI/POS is to go against their own interest if they try to mess with the blockchain integrity as they are the ones with the most skin in the game.