This is a very common question and there is a lot information out there to disect. According to Dr. Laura Robinson, DVM, there is a recent study that suggests raw dog food does not provide additional nutrition when compared to kibble and does not necessarily provide a nutritional benefit. Dogs on raw food diets can have chronic diarrhea issues, or different bacteria and viruses that are not apparent in dogs on other diets. That being said, there are dogs that do great on a raw food diet.
If you are contemplating switching your dog to a raw food diet, Dr. Robinson suggests treading very carefully, due to the lack of studies on long-term effects. It's important to consult with your veterinarian before making any changes to your dog's diet because not all dogs react to all ingredients in the same way.