I've used Felidae and Nutro Natural Balance. They both did fine, much much much better than on Purina, which made them puke a lot and have gas. Probably from the corn.
Felidae has no corn, but Nutro has a little. But it doesn't seem to be that much or bother them. I get Nutro Natural Balance now b/c I can't get Felidae locally. Well, I have to drive 60 miles to get the Nutro too, but that's ok!