Since I'm the natural nutrition junkie here....
Okay....first and foremost I want you to be prepared for the distinct possibility that there may be health issues and even death with any hatchery chicks, and especially those shipped through the mail. Shipping is extremely stressful for the chicks and sometimes more than they can handle. And hatchery chicks are typically bred in volume with minimal attention to declining genetic vigor.
Now, in regards to medicated feed: Centuries ago westernize medicine seized on the idea that disease and poor health comes only from outside of the body via such things as germs and viruses. This is what led to such things as pasteurization of food products, the discovery and production of antibiotics, etc. Medicated chick feed is part of this ideology and is touted as a preventative measure, which may or may not actually be effective. Especially in hatchery and shipped chicks, it is possible that increased stress could have the inverse effect of depressing the chick's natural immune system and make it more susceptible to exposure to viruses, bacteria and parasites. The medicated feed could potentially kill off those germs to allow a chick to recover.
The argument AGAINST medicated feed stems from an alternative theory that 1) disease cannot exist in a healthy body, and 2) any and all medications, while initially helpful in some ways, also have a significant and cumulative long-term negative impact on a living organism. This ideology follows the belief that by providing the optimal nutrition needed by the body, the immune system will naturally improve and result in a genetically stronger organism overall. This is also a bit of a brutal belief system in that it allows for the natural death of weaker specimens (which is essential for serious poultry breeders).
Which should you choose? Whichever makes you more comfortable. Nobody on this thread will chastise you for the decision you make because everyone here is very supportive and just wants you to have the best possible experience with your chicks.
I can tell you that personally, I've literally hatched hundreds of my own chicks and never used medicated feed and all of my birds have been healthy and vigorous, so don't be scared about NOT using medicated feed. But...if you feel that medicated feed affords you that little bit of extra protection, go for it!
Freaking story of my life, I swear! 
