There are an awful lot of pitfalls with judging a dog food by its ingredients list (which is what dog food comparison websites do) this article explains it better than I could. It was written by three Professors of Veterinary Medicine who are all Board qualified Pet Nutritionists:
vetnutrition.tufts.edu/2016/06/why-you-shouldnt-judge-a-pet-food-by-its-ingredient-list/
There has been a spate of newer, well thought of dog food companies who have lost lawsuits over falsifying ingredients lists so that they are more appealing to owners and so that they are ranked higher on dog food comparison websites.
There is also growing concern about grain free dog foods causing or greatly increasing the risk of heart disease. The FDA opened an investigation in 2019, and is still investigating, whether grain free dog foods either cause, or increase the risk of heart disease, Canine Dilated Cardiomyopathy.
For the FDA to actually do something, let alone open an investigation and still be investigating is really saying something too.
Through fostering I have seen so many people peer pressured into buying expensive, lightly toasted by the beating of Pegasus` own wings McFabulous trendy food, and then not be able to afford insurance, or a proper flea and worm schedule, or even proper vet treatment.
If you can be sure it provides 100% of their RDA of vitamins, minerals and nutrients for their correct size/breed/life stage, if your vet* (provided you trust them) is happy with you dogs health on it and if you can afford it and you are content with it, thats all you really need.
*Obviously if your vet tries to upsell more than a cartoon used car salesmen, get a second opinion, and change vets. You need a vet you can trust to be impartial, and to have your dog`s best interests at heart.
Far too often dog food ingredients lists are made to look appealing to the owners, regardless of whether they are actually better for the dog or not. What sounds disgusting to us can be fantastically nutritious for dogs, offal for one, which comes under the banner of animal derived/animal by products.
PolePup gets Purina Puppy, it suits him very well. PoleDog (my giant breed working dog) gets the dreaded Pedigree Chum chicken as it is the only dog food he will actually after trying everything else under the sun. Every dog will be different 