<p>Caltech, unless you want to go into pure academia, in which case you might consider Stanford. Stanford will probably have you teach undergrads several hours a week for the years not covered by the scholarship, so you'll have a chance to compete for teaching awards and the like, which will be useful additions to your CV.</p>
<p>Doesn't matter which one you go to, but just in case you don't receive an offer from MIT, choose the school where you'd like to study for the whole PhD program. In any case, it would be useful to stay with the same graduate advisor.</p>