I don't think we know enough about what constitutes benefits for corals like you might be meaning.
And I guess 20k vs ??
10K came first, so 20k arguably offered the benefit of a somewhat more realistic "blue-heavy" light environment for the corals. There is that. :)
Also, I think Sanjay Joshi did some comparative studies on corals grown under 10K and 20K (others?) and 20K pretty much universally colored corals better...or allowed them to color better....whatever. :) That's the part we don't really know....is more color better? Or less? When is my coral "happy"? LOL.