I feed non-medicated. I can get a really good, locally-milled, non-GMO feed with whole food sources of vitamins and minerals instead of synthetic, and I personally feel the benefits of a good food outweigh potential benefits from medicated. I also am not sold on the benefits of medicated feed anyway. I've read many stories of people whose chicks got sick anyway, and I would rather my chicks build up a strong, healthy immune system on their own.
That being said, my chicks actually do have Coccidiosis and I lost one yesterday. The rest seem to be okay. Next time, I will have medication on hand just in case (I couldn't find any so wasn't able to treat them right away), and I would put dirt in their brooder from very young so that their first venture outside isn't the first time they are exposed to all the germs. I still wouldn't feed medicated feed though. I would rather medicate them as needed than medicate "just in case". I also wonder since the medication in the feed is Amprolium and the most recommended medication is Amprolium if the chicks that do get Cocci anyway are more likely to be resistant to the Amprolium, meaning the harsher stuff would have to be used. If I had breeding stock, I'd probably be even more selective about medications because I would want to breed the healthiest, strongest chicks only anyway.