Well, the Metal halide version would be better for coral, but it can create excessive heat, and that creates its own problems. ( need for a chiller )
The regular version, I think comes with compact fluorescents, this would probably be OK for some soft corals, but that would be about it.
I really don't know too much about the cubes, and maybe someone with first-hand experience with them could tell you for sure.
I believe that the CF
version would work for soft coral, but I'm not positive.
Sorry I can't be of more help!