i've eaten at both. after we went to ohana's, we went back to it rather that back to 1900 park fare.
they're both good, but i like the whole experience at ohana's more. for one 1900 was a buffet, when we were there. maybe they've changed that but i don't know.
at ohana's they give you the most delicious juice! they bring the food and it just keeps coming. and it is soooooooooo delicious! they have great fruit, and all the breakfast food is yummy.
maybe the main thing for us is the parade and all the fun the kids have. both restaraunts have characters, but the kids have a great time in the parade.
hope this helps! whichever you choose, you'll have an excellent meal!