This is interesting because, from my understanding, the two offer different experiences in terms of ambiance. I've eaten at CG twice and both were what I'd call fine dining. I easily could have been in NYC and felt quite spoiled by the whole thing.
At Kona, while I've not dined there, I understand it to be less upscale. I suppose you could argue that from the 1 TS credit issue alone. I have heard great things about this place and look forward to trying it, but I would expect to have an experience rather like going to a favorite, great-food local place. The CG is one that, IMO, you can't get "just anywhere." I think you'd have a great time with great food at either place, so for me, it'd be about the type of "atmosphere" you're craving that would be the deciding factor.