Tusker House for sure, we did both last trip. Ohana breakfast is very normal...there is nothing special about the food that differentiates itself from other restaurants. Sausage, bacon, seasoned potatoes, scrambled eggs, Mickey Waffles...you do get some sweet breads that are possibly unique. At Tusker House they have all kinds of interesting food that I haven't found at other breakfast places at WDW. At TH, you can get normal food for picky eaters and then get some more adventurous stuff with African flair for those who want that. I was surprised when we did Ohana for the first time this year and found that there wasn't anything unique about the food...it was good, but there is nothing there that you couldn't get off of the buffet at CP, TH, and most of it is available at Akershus. My kids love the juice that they serve, but it is actually the same at both restaurants according to our Ohana server.
My family loves doing the large breakfasts before park opening, another possible advantage of doing TH is getting into AK early. We went to Ohana on a non-park day, so that is an advantage to eating there.
Enjoy!