While I imagine there is some overlap between the advisory services ibanks offer and MCs (I know a couple people who work in Deloitte's M&A practice), for the purpose of your apps you need to be specific. The box you check in your app doesn't limit what you can pursue at bschool, but appearing indecisive will probably hurt your admissions chances.
IMO, choose a path you can write passionately about for your apps (sounds like boutique IB for you) and then worry about the details on campus