First of all, how would they really know if you applied to both. There are two different application services for each, so unless you told them or you live in Texas where the same service is used to apply for both then I dont think they will ever know. Many people apply to both MD and DO, even people like me that only want to be a DO, and get in to both or either so I dont think it really hurts your chances or makes a big difference. I would not worry about this very much, you have much better things to worry about if you are applying to med school.