I've never been to Chef Mickeys, but I do like Ohanas character breakfast.
I really perfer family style when small kids are involved (or I don't eat, I just keep going to the buffet for different food for a different kid).
We found the character interaction a Ohanas to be wonderful, the food to be very good (the pineapple bread alone is worth it). All the characters came around (Mickey, Goofy, Pluto, Chip and Dale) to the table and had a photo op with everyone in the party (six of us). The were also very sensitive to the differences in my children - my two year old daughter who treated all characters like living stuff animals to hug (btw, how do they keep Chip's checks from being covered in maple syrup?) and my son, who perfered a little more space when confronted with a five foot tall chipmunk.
Chef Mickey's books faster. Which means if you postpone getting your PSs, you might be at Ohana's anyway.