Kona has far better food, and is definitely a more "adult" experience. Ohana is good for a kind of cheesy show, and large quantities of poor-to-mediocre food. You choose. A recebt Dis Unplugged podcast featured both a review of Ohana's and Kona. You can find it here:
http://www.wdwinfo.com/disney-podcast/archives.htm
Scroll down to the September 11 edition, and click on "Listen Now" or download it to your computer. If you haven't listened to the podcast before you may enjoy its irreverent-but-honest tone.