As these are my two favorite restaurants at EPCOT, it's a tough choice. I got the meal plan with my package and plan to do the CP package, which includes dinner. I was thinking of doing dinner one night at Le Cellier using the meal plan, then dining at the R&C using the CP dinner package. This way I can take that meal and use it towards dinner one night at the California Grill.
Both restaurants are very good and I think it will depend on what you think you would enjoy more. Deb Will's site has complete menu's for both places. I'd take a look at these and see if there is something everyone would enjoy.
If you decide to do the R&C, plan on making a PS around 7:30pm for the 9pm Illuminations show. Stop by the desk early in the day and confirm your PS and tell them that you would like a patio table. Show up to your PS early, reconfirm your wishes for a patio table and tell them you don't mind waiting for one. This way you can enjoy a great meal ,then relax and view Illuminations over a great dessert.