Pedro is on a vet prescription diet as he has had lots of food allergy problems. He can only tolerate venison/potato food. The vet prescribed one is Royal Canin Venison Formula Limited Ingredient Diet. His vet is at the Petsmart/Banfield place and not only do I want to change vets soon, but I also want to change his food to either Natural Balance L.I.D. Sweet potato & Venison Formula or the Nutro Adult Natural Venison Meal & Potato Formula. My question is that I'd like to know if the Nutro and Natural Balance is just as good or better for Pedro than the vet prescribed one and is there any difference at all between the vet prescribed and the other two?