I work at a holistic dog-food carrier and bakery so I can be of some assistance. I've done my homework
1. Wheat, corn, and soy are not the best ingredients to give to your dogs, which is why we often stress switching over to Holistic food. Holistic = free from wheat, corn, soy, chemicals or by-products.
2. Any holistic food will help your pup achieve a better health but specific brands specialize in various things. It's really what a. you pup likes and b. you want for them.
3. I highly, highly recommend Innova's EVO brand. It's a grain-free, high-protein diet that is top quality. It's giving your dog exactly what it needs and nothing else: no filler or unnecessary garbage. ** My B, Shango's on EVO and eats it right up and he's quite the picky eater. EVO gives him a beautiful coat, higher productive energy levels and fewer and smaller stools.
4. While I don't feel that non-holistic food is 100% terrible, (Actually, some foods that are non-holistic are quite good!) there are some things to consider. IAMS, however, is quite a bad choice for dogs. Especially for dogs with sensitive stomachs or particular needs. I'd recommend researching the danger of IAMS as PETA and other organizations have done extensive research and found some pretty startling statistics.
Hope this helps. Let me know if you have further questions.