Judging a food by its ingredients list has a lot of pitfalls, this article explains why:
vetnutrition.tufts.edu/2016/06/why-you-shouldnt-judge-a-pet-food-by-its-ingredient-list/
Its a US article, but it was written by three Board Certified Veterinary Nutritionists, who are also Professors of Veterinary Medicine and run a clinic, so not just another random opinion.
There are also concerns about grain free food greatly increasing the risk of heart disease (dilated cardiomyopathy), the FDA opened a case in 2019 and are investigating. A lot of vets, mine included, will not recommend grain free dog food.
There are also a fair number of lawsuits won against so called grain free dog foods for falsifying ingredients lists.
Our vet has always said to look for a food which covers 100 per cent of their RDA of vitamins, minerals and nutrients - and do check with your vet that the claim works for your dog as all are different.
I have fed grain free for one of my fosters, it was the only food she could tolerate, I have fed raw, I have fed homemade and I feed PoleDog plain old Pedigree Chum.
The best dog food is the one your dog will eat, that your vet is pleased with them on and that you can afford.
Not sure about the UK, but here there seems to be a growing amount of snobbery about dog food, and that if your dog isn`t on the most expensive, everything free diet you are a monster and animal abuser.
I have seen a lot of people feeding expensive dog foods only to not be able to afford a proper flea and worm schedule.
Its awful, as every good owner wants to do the best for their dog, and there are many different parties trying to cash in on that, as with anything it is very hard to get impartial information.