I would personally vote for Chef's because I love the atmosphere, food, light and bright dining room. And our three boys love meeting Remy at lunch, and the CM who "assists" him was wonderful. She and Remy spent a lot of time at our table. We were just there on Tuesday for lunch and it was great. If you are making an ADR for dinner, I would still recommend it.
We were at Coral Reef on Wednesday for lunch, and also enjoyed it. Our older boys are a little older than OP's daughter and didn't care for the child's menu much - primarily because the meaty macaroni has lots of onions in it. But they did enjoy the chicken noodle soup and the make-your-own sundae dessert. My husband and I enjoyed the food and our boys liked the view of the tank. We'll probably return, but I definitely prefer Chef's.
But it depends on your interests - if your daughter is really into the aquarium theme, for example, Coral Reef was good. If she would enjoy meeting Remy and you are going for lunch or any early dinner, then Chef's. In my opinion, if your choice is based on food quality, I'd suggest Chef's.
Good luck with your decision!