Diamond is one of the largest and oldest dog food manufacturers around and sells the foods under many different labels. They have had some recalls in the past on certain formulas. People have varying levels of trust in the company as a whole.
They sell Diamond and Diamond Naturals under their own name. They also own, make and sell: Taste of the Wild, Chicken Soup, Premium Edge and Professional. They are under contract to make the food for: Solid Gold, Natural Balance, Canidae, Costco's Kirkland and perhaps others.
I tend to look for formulas made by smaller companies that only make pet food and control the process from beginning to end. I look for meat-based quality protein sources and very few fillers, if any. For puppies, I wouldn't want to feed a formula with any less than 25-27% protein and a minimum of 15% fat.