I am going to throw it out there that I am no expert and have never even owned chicks (getting our first ones next week!!!). But, I talked to a farmer for awhile yesterday about medicated feed when I was deciding what to do. He told me not to. He said the best analogy he had was giving a newborn penicillin everyday. Sure, they won't get sick. But they also won't be able to build up their immune system. Once you are done with the medicated feed, they are more susceptible to sickness. Not sure if this is accurate, but he sure seemed to know what he was talking about. We are not going to do medicated feed, but will medicate a chick if needed, not the whole bunch.
I agree about not using medicated feed in dryland Colorado. Coccidiosis is more prevalent in wet areas with more moisture than seen inCO. Though if your ground has harbored the disease then yes use medicated. But theres definitely value in letting animals build immunity. I had read that if a person always helped chicks during hatching, the birds develop inability to hatch on their own.