You can try, the honestly level and acceptability of that action probably varies from place to place. My school encourages students to share with us what they are looking for from a program and to tell you if we or another school will help you get there. But I doubt every school is like that. Play it by ear, basically.
Also, it sounds like the two schools may be very alike if students can't pin down specific reasons. If you REALLY can't choose, I'd say go with Tufts, since you get better name recognition outside of the region, but that is a completely uneducated opinion.