I know you're debating soybeans vs. not-soybeans, but just remember, RAW soybean is toxic to chickens. Soybeans must be roasted first before used as feed.
Denali,
I buy my feed from a local farmer who grows and mixes his own feed, and pastures his chickens (both broilers and egg-layers).
His egg-layer feed mix is corn, oats, roasted soybeans (unroasted soybeans are toxic to chickens), with a Probiotic (important) and a vitamin/mineral mix...