The idea of choosing dog food which is the best suitable for your pet by trial and error method is like using humans as a guinea-pig to perform experiments. Your dog trusts you and it can’t say that it feels unwell after eating the food you have chosen.
Though, it is true that dogs get used to any food quite easily, except some products (chocolate, for example, which is toxic for them). But, the right dog food contains all components in necessary proportions for your pet to grow healthy. If you love your dog, you won’t feed it with junk food.