Feeding Chickens and where to source the food. Feed Stores or Grain Mills?

Hello everyone we are going to discuss the different options available to most chicken owners and the pros and cons of those feed sources.  There are reasons to buy feed from feed stores of course as well as there are reasons to buy locally sourced grain directly from the mills.  The biggest argument I have ever heard is that the flock owner is conditioning their birds for shows.  Can this theory be debunked and are there any listeners that would like to give their experience as to whethr or not this theory has already been debunked.