We did both these restaurants just last month.
Ohana was one of my favorite meals. I'd describe the food as fancy, quality BBQ. So much delicious stuff that kept coming in rounds. I wished I had more room! (Save room for the dessert!) It was neat to have it served family style too. The noodles were a huge hit at our table. My only minor complaints of Ohana were that the seating arrangements seemed overstuffed and cramped. Also, we had a Sat 6:30 reservations and it was the only place we had to wait more than 10 mins to be seated (prob 30 mins). The extra wait may have been a good thing b/c at the very end of our meal the Wishes fireworks started and we watched them from our table!
1900 Park Fare was good b/c of the character interaction. I thought the food was better quality than the average buffet, but it seemed to me there were more cold, upscale salad type options (some seafoody) than actual hot dishes. I liked that the desserts were in very small portions so I could sample everything without wasting. The strawberry soup is truly delish!
If I had to choose where to rebook for our next trip, I'd choose Ohana.