Neither place is quiet. 'Ohana is rowdy with coconut races, hula dancing, and a microphone wielding hostess. Kona is noisy because it's open to the Poly lobby.
We have had lunch and dinner several times at Kona, and we've had dinner three times at 'Ohana.
We prefer 'Ohana for dinner. We've had a few disappointing meals at Kona as well as some pretty lousy service there as well.
'Ohana is in my view very "Disney." Silly, loud, kind of cheesy (though I don't believe they serve cheese any longer!) and usually good though not gourmet food.
I think Kona is better for lunch than it is for dinner. It is more ambitious in its menu, but in my book, the quality is not consistent.