That's a tough one!!! Those are my family's two favorite restaurants in Epcot!
They are both delicious and while I agree with the earlier responer, I would also like to mention that my young ones definitely enjoyed Teppanyaki more because of the entertainment value of the chef. My youngest dd was 3 then and our chef was amazing. They still talk about eating their ice cream dessert with their chop sticks! It was really fun.
You just can't go wrong with either choice!
Have a great trip!