Ok i am a little confused, because Lexie has crystals the vet has recommended Science Diet C/D, but others mentions Royal Canin which i can obtain as well, so please can anyone give me the facts on both and why SD has been unpopular for some and not others, i really do need to make the right choice here for Lexie, Royal Canin might be a little cheaper, but there is not much in it for me, i just want her to have the right stuff that will work.