Off the top of my head, I'm going to say CSCL. RC is typically rather crappy food.
But let's look, shall we?
RC:
Chicken meal, corn gluten meal (BAD), chicken fat (naturally preserved with mixed tocopherols), brewers rice (BAD), chicken, corn (BAD), pea fiber, beet pulp (sugar removed), natural chicken flavor, salmon oil, potassium chloride, zeolite, dl-methionine, chicory extract, dried eggs, choline chloride, borage oil, brewers yeast extract (saccharomyces cerevisiae fermentation solubles), ascorbic acid (source of vitamin C), vitamin E supplement, dicalcium phosphate, taurine, marigold extract, zinc proteinate, glucosamine hydrochloride, folic acid, biotin, zinc oxide, ferrous sulfate, l-carnitine, niacin supplement, manganese proteinate, chondroitin sulfate, calcium pantothenate, iron proteinate, copper proteinate, green tea, grapefruit extract, copper sulfate, manganous oxide, vitamin A acetate, riboflavin supplement (source of vitamin B2), pyridoxine hydrochloride (source of vitamin B6), rosemary extract, sodium selenite, thiamine mononitrate (source of vitamin B1), vitamin B12 supplement, calcium iodate, vitamin D3 supplement.
cs:
Chicken, chicken meal, cracked pearled barley, chicken fat (preserved with mixed tocopherols), ocean fish meal, white rice (NOT GREAT), potatoes, oatmeal, millet, natural chicken flavor, salmon, turkey, duck, flaxseed, sodium bisulfate, egg product, methionine, potassium chloride, choline chloride, dried chicory root, taurine, kelp, carrots, peas, apples, tomatoes, blueberries, spinach, dried skim milk, cranberry powder, rosemary extract, parsley flake, yucca schidigera extract, L-carnitine, Enterococcus faecium, Lactobacillus casei, Lactobacillus acidophilus, Saccharomyces cerevisiae fermentation solubles, dried Aspergillus oryzae fermentation extract, zinc proteinate, vitamin E supplement, niacin, manganese proteinate, copper proteinate, zinc sulfate, manganese sulfate, copper sulfate, thiamine mononitrate, vitamin A supplement, biotin, potassium iodide, calcium pantothenate, riboflavin, pyridoxine hydrochloride (vitamin B6), vitamin B12 supplement, manganous oxide, sodium selenite, vitamin D supplement, folic acid.
Yup, I was right. CS is a much better food. It's not grainless but at least it doesn't have corn and it does have more actual meat.