I had Bailey on Royal Canin from the time she was 10 weeks old. In Nov at 19 mo, I had to switch her to a different brand because of developing food allergies from RC. Royal Canin has corn in it. Our vet used to carry RC in her office but has switched brands in the last few months because of all the problems she was seeing in her patients.
Iams is not a very good food, and they also do animal testing, here is the link.
www.iamscruelty.com
There are much better foods then both of these. Go to a local pet food store (not Petco or Petsmart) or feed store and ask for samples of different brands to try.
Here is a link for quality dog foods:
http://www.dogfoodanalysis.com/dog_f...ndex.php/cat/1
Good luck