Bias: Very content Vanderbilt MBA student here.
Are you going to stay in TN after you graduate? If yes, choose Vandy.
Are you going to stay in your same job and/or industry after you graduate? If yes, choose Vandy.
Are you price sensitive/averse to debt? If yes, choose Vandy.
**IF** you're a career switcher, Duke will be a better option. **BUT** if you're a career switcher, you're crazy to do an EMBA/Evening EMBA/PT MBA. Go full-time wherever you go would be my advice.
Also, have you visited both schools? If at all possible, you should. You might really like one culture better than the other.
In my experience, Vanderbilt has an equal amount of brains that the elite East Coast schools have, but it is paired with Southern hospitality and Midwestern goodness.
Duke on the other hand has a more competitive, edgy, and elitist streak running through it.
One final thought...take a look at the faculty of both programs. One school may have better professors (read: better matching professors) for the concentration(s) you're most interested in.