You'll get a lot of pro NSU votes here because it is the more established school. MU wowed me ten ways from Tuesday. So much so that I ended up committing to it over older schools...some would even say "top tier" DO schools. Being part of an inaugural class offers some awesome opportunities...but beyond that, the program that MU-COM has put together is rather impressive. The state and healthcare community support, the hospital/research affiliations and the fact that it is one of only two medical schools in the state make for a unique atmosphere. No school has even come close to matching the level of involvement and support towards students that I have seen from MU-COM.
In the end it really boils down to a personal decision. There are SO MANY factors that play into which medical school to choose when you are lucky enough to have a choice in the first place.
Make a pros and cons list and add to it as you think of different things. That way when the time comes to make a decision you will have a tangible reference to resort to.