Personally, neither. You feed what your dog does well on. I just don't like the ingredients in either food and prefer to go the more natural food route.
We feed our dogs Pro Plan Lamb & Rice. They do very well on it. But I don't know that I can recommend it over Diamond because I've never tried Diamond.
I fed the pricier foods (Canidae, Innova, Wellness, etc...) and all I got was big loose poohs. I loved the ingredients of the holistic, expensive foods, but Pro Plan Sensitive Skin And Stomach Salmon formula is working great! Small stools, great coats, no smelly ears, no skin issues. (AlthoughI didn't have a lot of those problems to begin with). The food is reasonably priced, and all 5 do great on it.
I use the ProPlan and all my dogs do very well on it. I mainly use the ProPlan Sensitive Skin and Stomach formula. The main meat ingredient is Salmon and it puts a wonderful coat on my dogs. For my bitches in whelp and lactating, I use ProPlan Performance. They have a great breeder's program. Email me if you have any questions about it.
Best,
Marci
Pro-Plan now has a line of food called Selects. My dogs have been on the Salmon and brown rice and doing very well. I have tried all the holistic brands including one brand that cost $55.00 for 20lbs....and my dogs seem to be tolerating the Pro-Plan Selects much better than the other food I have tried. I guess you have to go with what works best for your pack.
I had great results with the PP Selects Salmon too. No corn gluten meal in that formula either.
I recently switched over to Nature's Variety Prairie Salmon formula (and have since moved to chicken - the 4 varieties are able to be freely rotated)because I was able to get a bulk discount from the local feed store. For the first time, I have all my dogs on one food and it's wonderful. Nature's Variety claims that their Prairie line has 40% meat and that the grains in it are grown right here in the U.S.