I have heard many bad stories about the 12000K Sunburst. I have been using it since they first came out. I happen to love it. It gives a great color to the tank, not bright, but a blueish tint. I think that I will stick with it. I find that the 5500K and 6500K bulbs are too yellow. I have not tried the 10000K, and may try them on my other tank when it is finished.
The bubble corals and meat corals really spread out under it, and do well. Mushroom corals do not like a lot of light, but they seem to like the sunburst bulb if kept out of it directly.
I was truely impressed when I saw the shimmer of the light when I first turned it on.