I went with DiveMex last time I was in Playa. Pricing and what I read on the CenoteXperience website sounds like they are similar to DiveMex. The only big difference for DiveMex is they are on Calle 2 and CenoteXperience is on Calle 34 (the ferry docks near Calle 1), i.e. DiveMex is walking distance. You might want to see if someone can pick you up near the ferry if you are going with CenoteXperience.