There are different types of tasty varieties are available for the dog. Many companies add new flavor in each month in different types of foods. If you are serving different flavor food than your dog will habituate with different types of flavors.
It is necessary to see the content of the dog food to know that the dog food contains enough nutrition. Some time dogs are more habituated with different types of taste so you do not want to give different flavor so that the dog do not overeat the food.