You can grow corals beautifully with any of the fixtures listed so I think it's going to depend on what your expectations are and what is most important to you. If you want the completely polished and beautiful interfaces I think the Radion would be ideal, and the Hydra close behind. The Rapid LED Corona may be more energy efficient than the RB or SB lights since the rapid fixture is using CREE leds and I'm not sure what the SB and RB are using, but the hydra and Radion will also have CREE.