My family has eaten at Donald's and the buffet is great for selection. Standard hot buffet foods (my DD loved the chocolate chip pancakes!)plus the cold fruit bar with cereal and breads was great too. We left this breakfast very satisfied. We had an early ADR (before the park opened) and were finished just about when the park opened. It was great to be there that early (even if it was a little chilly - we went in January)
The meal at 'Ohana is served family style (eggs, bacon, sausage, potatoes, mickey waffles).
Unless you just want to let the characters dictate which one - Donald is at his own breakfast, but Lilo & Stitch are at 'Ohana.
I guess it depends on where you're staying as well and travel time. Donald's requires park admission for the day, but not 'Ohana so it's good for a non park day. AK is a little further away from most onsite resorts.
All that said, we've done Donald's, so we're trying 'Ohana this next trip. For children's entertainment value you can't go wrong either place (I don't think it's a bad menu at either place).