Some people raise chicks without medicated feed, and never have a problem. Some other people have outbreaks of coccidiosis. I suspect it's a matter of climate, and exact details of the brooder setup, and maybe a few other things I don't know about.
If you try un-medicated feed, and if your chicks do get coccidiosis: there is a medicine called Corid that can be put in their drinking water to treat it. (Coccidiosis is not an instant death sentence--prompt treatment can save the chicks.)
Ultimately, it all comes down to what you're more comfortable with. But either medicated feed or unmedicated feed can be a reasonable choice.