This is a question I did not believe I needed to think about. Organic, of course, as I would prefer my dollars pay for sustainably raised grain. However, after trying a variety of different feeds for my small backyard flock (from 3 different farm stores), I have determined there is a more important feature of chicken feed - whether its in pellets or "mash". Mash is very powder-like. Hens make a mess of mash. A fair percent just ends up on the floor, never to be eaten, which then requires clean-up. In a small urban henhouse, cleanliness is the rule. Chicken feed scattered everywhere is a recipe for rodents. Rodents can even be attracted to the compost bin when spilled feed is added. So pellets it must be. The hens are much less prone to toss pellets into the far corners of the henhouse, and any that do get spilled are easily pecked right back up. Trouble is that I have yet to source an organic feed that comes in pellets.
So for now the hens get conventional feed. This is not a permanent situation though. I actually would prefer to eliminate corn from their diet entirely. Humans have created the corn diet for chickens, just like we have a corn diet for ourselves, cows, pigs and every other domestic and farmed animal. A long-time goal around here is to expand our vermiculture to also feed our hens. We are not the first to try this and we realize will be a while before we have enough worms to feed and compost. In fact, we may have to reclaim additional food waste to actually achieve this goal as the current population of worms and hens is taking care of our trimmings at present. Needing more food waste is a delightful problem to have for those of us who are concerned about organic waste in landfills and the methane it creates.