My family has eaten at both, and both are great, but we very much prefer Kona. The variety of food suits our family and the atmosphere was lovely. Brighter, less "Poly" (in my own opinion) than O'Hana's. We ate there on the very last night of our 2002 trip, and I still remember how wonderful it was. Can't wait to go back. Not only was the food terrific, the service was great, drinks were excellent, and the atmosphere was comfortable.
Either way, you can't go wrong.
Enjoy!