Pick whichever menu appeals to you more. I've done both and while we preferred Le Cellier, I don't think it would be worth 2 dining credits, when you can basically get the same thing for lunch for 1. I think the thing that made it shine was the fact that we got a $100 meal for the equivalent of around $44 (this was back when the dining plan was only $39.99/adult).
Our Jiko meal was on our arrival night, and we ran into a bit of confusion when the check came.
I agree with the previous poster about your party. If you're trying to switch over the Jiko on the same night that you have the party, it won't get you there any faster than Le Cellier.