We have done both and they are both really good choices in terms of the food offered. If you are looking for a fun but more relaxing breakfast Ohanas is great - as previously mentioned the food is brought to your table. The kids get to parade around the restaurant with Hawaiian Mickey, Pluto, Stitch & Lilo. The character interaction was really good at our table and the photopass photographer did a picture with Stitch.
At 1900PF I thought that there was a wider selection of foods on offer which is buffet style. The characters are really fun. We particularly loved Alice, Mary P and the Mad Hatter. Here the photopass photographer did a picture with the Mad Hatter after our meal. If I had to choose between the two I would probably pick 1900PF as you get 5 characters (some of which are more difficult to meet elsewhere) and I love the Mickey Waffles with whipped cream and blueberry sauce!