These sites along with many others provide a decent source for information.
I would rather do some research than experiment on my dog with foods which may not be as good as others, or worse yet, foods made by a company with recalls.
Sorry, I totally disagree. The internet and the information espoused by their purported experts is one of the poorest ways to get information and do research.
As Mark points out, many are run by people who have an axe to grind, have no training in animal nutrition and just repeat unsubstantiated internet opinions.
Feeding trials (NOT EXPERIMENTATION) are the only way to really evaluate the worth of a specific diet.
In the end, what works best in each individual is the BEST FOOD for that animal.
Doug, DVM