We really enjoy both, although they are different experiences.
For Kona, we tend to do an earlier reservation, and then go down and enjoy the fireworks from the beach and get a dole whip. The food at Kona is awesome, and comes out piping hot. We love the pot stickers and wings for the appetizer. The sushi is very good and we both enjoyed our entrees, i had the pan asian noodles with chicken and DH had the coffee rubbed pork chop. Both amazing and tasty. We didn't do dessert as we opted for a dole whip later after walking around and settling on the beach for the fireworks. Now, with the new addition of the bungalows beach space is more limited, and sometime we end up watching from the Grand Floridian upstairs on the balconies instead, but its up to you!
As for O'hana. Our last experience was last month. We had a 745 reservation and were sat right by the window. Fireworks were at 9pm that night. The Bread was okay, not as warm as we had expected. The salad, wings, and pot stickers were AMAZING. The meats were good. DH found that they were warm but not hot, but the meat still tasted delicious! The noodles and veggies were good as well. But nothing compares to that banana bread pudding with the caramel sauce and watching wishes. I could eat plates of it.
Overall the food was good at both. I would say food was better at Kona, depending on what your looking for, but the atmosphere of O'hana is awesome. DH loved the meats at O'hana, where i definitely don't eat enough to make the price worth it on the meats.
Both good options though!