Hi and welcome to Purrs.
I'm assuming the binders are to help with George's kidney problems and not his diabetes? Both are phosphate binders and as far as I am aware either can be used with any cat food, be it specially formulated for cats with renal problems or 'normal' food. I have only ever heard of cats being prescribed either one or the other and while some vets will prefer Ipakitine, others will advise Renalzin. Often its down to which the cat finds most palatable.
Was it your vet who said to Renalzin with RC renal wet and Ipakitine with other food? If so, maybe you should ask him/her to explain why.