Pet food manufacturers cannot print "complete and balanced" on their food products unless it meet certain criteria that are established by the AAFCO (Association of American Feed Control Officials).
These criteria are met by either:
1) meeting a nutrient profile or,
2) by passing a feed trial
On the fine print of the packaging of any pet food product, there should be a little blurb about it being AAFCO approved.
If you would like to have more information on what kind of things you should look for on a dog/cat food label, you can try this website.
I hope this helps. Remember, your dogs are individuals and may be better suited to one dog food compared to the other. It doesn't have to be the most expensive food with the gimmicky ingredients to provide your dog with adequate nutrition.