I've been to both and I've been back several times since I really enjoyed both places. Either place you go, you'll have lots of fun, especially the kids.
If I had to pick one, I would say Whispering Canyon Cafe. Both restaurants are very interactive, but Whispering Canyon is one big room, so you see everything that's going on with the other tables, and everyone gets to join in on all the fun. And I love when people have to ride one of the ponies. One time, my friend in our group who was 21 had to ride it because he was the only one who had never been to the restaurant before. It was a riot watching him ride around the restaurant. Also, we all really seem to "pig out" at WCC because we always order the skillet and keep getting refills, and we love the bottomless milkshakes and large sodas!