Honestly they are both really good lights, I have heard a lot of positive stuff about the R15Pro. They are to expensive for my blood but they do a good job of growing corals.
Not sure abut the other led's out there but I can honestly say the radion x30 I just exchanged for my hydra puts the hydra to shame. But you need to look and spec out the coverage as the hydra is wider than the x15, but depends on your tank size and such. They are both great lights, but the radion is the Ferrari for sure.