We have eaten in both restaurants about 30+ times.
Out of the two I would have to go for the Hard Rock Cafe:
The HRC is fun, has a great atmosphere and the food is great too. Especially the Jumbo to share and a NY strip or the fajita combo. The place is loud, but thats adds to the atmosphere. They love repeat customers in this place and will always go out of their way to make you feel special. The last time we were there the manager came over to our table and said the meal was on the house. She even gave our 2 year old daughter a personal tour of the cafe! When we returned she had a present ready to give her.
The Kitchen is another good themed restaurant. A bit quiter than the HRC, but still has a good atmosphere. The food is is slightly more upmarket and more expensive. We have ocassionally seen a few Universal characters (scooby and Woody) in there. It has a great childs play area at the back of the restaurant. If you go there for breakfast, it can work out quite expensive.