Well, it depends on what you are looking for, mainly. They're all fairly similar ingredient wise... the guaranteed analysis' are pretty similar.
So then it comes down to choosing your company. Wellness has a formula or two manufactured by Diamond which some are uncomfortable with. Most of their food is made at Old Mother Hubbard though I think. I like Wellness personally, but never had luck with it. Gave Jackson goopy ears and lots of poo.
Blue Buffalo is another hit-or-miss, IME. Some love it and do really well on it... I often read of gas or GI issues with BB. Their food is made in like 5 different manufacturing facilities.
I use Acana and really like it. We've often tried others and then we always go back to Acana. I like their company for the most part... they are all made in their own facility, I like their customer service, and their ingredients. Most of all, my dog loves it and does very well on it. 2-3 small firm poops a day, hardly any eye goop/boogers, his coat is always soft and shiny, teeth look good, digestion is great, etc. Just our experience, but every dog is different and will do well on different things.
