With our hound, she was on Pedigree Gold when we got her from the breeder. We kept her on that for a while after we brought her home and noticed she seemd to have dry skin...you could see it flaking on her black coat. We'd wanted to change her to something better anyway, so decided to go ahead. We started feeding Origen. She ate it, no problem, but we didn't notice a change in her skin. After she'd been on it a bit, we started noticing that she acted kind of stiff when she moved about. Also started to notice brown spots on the grass, but attributed it to grub worms or something. A blood draw revealed her uric acid levels to go up to a high level. Excess acid was being expelled in her urine (thus the brown spots we discovered) and was storing up in her joints, thus the stiffness. The vet told us it was caused most commonly by a diet consisting of fish, eggs, liver, and green veggies. Well, guess what....no more Origen for her.
So onward to something else...tried Wilderness and Innova and Eukanuba. She ate just enough of them to survive...barely. I kept thinking she would give in and eat them when she got hungry enough, but after she came close to bones poking out and no energy and hair coming out in your hand when she was petted, I said enough was enough. So I started mixing in homecooked food with a bit of science diet that the other dogs were eating at the time. Well that would run right through her and her weight was still too low. We took her in to have her teeth cleaned as her breath was horrible and even I could see they were in bad shape. The vet told me point blank that whatever she was eating was not doing anything for her teeth and if it kept up I could look at having them pulled in a few years.
So, back to the Pedigree Gold (where we started), added with some homecooked, but not as much as before, Flax Oil (which has done wonders for her skin, coat and eyes!), Glucosamine for her joints (Bassets too can get all the help they need there) and a few other dietary supplements and occasional other 'human' foods.
She is healthier than ever now, has a great, thick coat, is energetic, better teeth and is at a healthy weight without excess fat.
So honestly, you can tell me I'm poisoning her by feeding Pedigree until the cows come home for all I care. I am less concerned about what's going in her and more concerned about the end result, which is finally a happy, healthy Flash, Trixie, Lexi and Chipsie...THAT is what matters to me.
But again, this is what I have determined is best for MINE. And it took alot of trying new things and dealing with what those that didn't work dealt us. It won't be what's best for the next dog. But given my experience, I don't think it's safe to assume that any 1 type of food or diet is what should be declared as 'best' for every dog across the board. That is where research and careful consideration for the dogs and their individual needs come into play.