We have been to both of these restaurants many times. Actually we make ADRs for both EVERY trip.
We love the mushroom filet at Le Cellier as well as some other menu items like the cheese soup, pretzel bread, etc. But now that they are scheduled to become a signature dining experience, I just don't see the "experience" in it. Don't get me wrong, we love dining there, we just don't consider it an "experience".
Now the Cali Grill is another story. We do consider it a dining "experience" when we dine there. The cuisine is excellent; from the sushi which is top notch to the desserts, which are heavenly. The signature pork entree is tender and tasty and the scallops during our last visit there were some of the best we have EVER had. The menu is forever changing which adds to a new dining "experience" every visit. The flat breads and lobster risotto is a must have as well. Did I mention the sushi?! The Spicy Kazan and the Tuna Three Ways are fantastic.
Now with all the rave reviews of the above metioned menu items, add a spectacular view across the Magic Kingdom (especially at sunset as mentioned by a previous poster) and the magic of Wishes

and you will have certainly had a dining "experience".
Obviously my vote goes to CG.