We've been to both. I much prefer Tusker House to Ohana. But it really depends on what you want and which characters you like.
Ohana is better if you are planning on MK that day. You can have an early bfast and catch the monorail over to MK. Characters are Lilo, Stitch, Mickey and Pluto. Bfast is a sit down meal served at your table of eggs, bacon, sausage links, melons, potatoes, waffles, pineapple bread. I wasn't too crazy about the food, I much prefer a buffet. Mickey wears a hawaiian shirt and the other 3 wear a lei. They have a parade and hand out instruments to the kids.
Tusker House is great when you are planning AK that day. Characters are Daisy, Donald, Mickey and Goofy wearing safari clothes and hats. Tables are dark wood and animal pictures are on the walls. They also have a parade with musical instruments. The buffet was very good and lots of selection of hot/cold foods and cereals/pastries.
You can check out my Oct trip report link below for pictures of the characters. We went to lots of character meals that trip.