Crystal, you know that old saying "you are what you eat" well the same thing is true for dog food. Many cheaper brands are basically fill (corn, wheat etc) and don't provide enough nutrition for our dogs. If you do a google search on the internet you would be surprised by what is put in dog food.
Many experts believe what we feed our dogs will help to fight future diseases just like in humans. Dog food is not an issue of "brand snobs" but what is healthy for our little ones.
Here is a little summary from Whole Dog Journal of what
to avoid:
DO NOT BUY foods that contain low-quality ingredients such as "animal
fat", "animal digest" or "meat meal" such as Purina Dog Chow, Cycle
and Gravy Train; products whose protein is derived almost completely
from "meat by-products" such as Cesar and Alpo; products lacking
understandable expiration dates; foods containing artificial colors
such as Purina's Beneful and Science Diet's Nature's Best; products
containing "meat and bone meal", a very low quality protein source,
such as Pedigree Complete Nutrition and Dad's; foods that are
sweetened to tempt a dog's appetite such as Kibbles 'n Bits and
Purina Dog Chow Senior 7+.