I'm not familiar with the XR15, just the XR30, does it have a "deepwater" setting or something close to that name? I can't remember for sure the name, but whatever it is, that's my favorite setting.
It's on the blue side. Be wary of cooking your corals with white lighting. Even the blues will cook them if you're not careful. High growth sounds like more white than blue. I'm not familiar at all with the Orbit fixture, but I would be thinking the Radion will have higher output. I'd probably leave the Radion at 45% for a couple weeks and see if you get any signs of bleaching, then adjust it yourself rather than relying on the Radion to do it. I wouldn't go up more than 3-5% per week after the first 2 weeks of adjustment.