We've eaten at both places, and I MUCH prefer Crystal Palace. Here are my reasons:
Crystal Palace - love getting an 8am ADR and getting into the park before it opens. I like their buffet, plenty of food choices for hot/cold selections. For my taste, I prefer a breakfast buffet to the Ohana fixed plate. I think the food is better quality and the atmosphere is more festive.
Honestly, the only thing I don't like about Ohana is the limited food selection. They have a separate server that comes around to serve the Mickey waffles which is the only thing my kids will eat there. Sometimes that server doesn't come around for a while and my kids are hungry.
That being said, any character meal at Disney is a wonderful experience. If you kids are into Lilo and Stitch, this is THE place to take them.
Have a wonderful trip!