This is a topic I have been researching for sometime and there are sooo many differing opinions it can really get frustrating trying to find the 'best' food for your particular kitty.
I have issues with two of my cats, one being very overweight and the other has allergy problems, so I have really been studying different foods trying to find one that we all can live with.
I came across this very informative website Basics of Feline Nutrition that really helped me understand just exactly what a cats dietary requirements are and how vets aren't always the best ones to get food recommendations from.