<p>Assistant professors are generally younger, and it’s not unusual for an assistant professor to spend more time at the bench and with students than a tenured professor. Of course, it’s not universally true, and you’d get more reliable information by asking individual professors how often they meet with their trainees or (better) asking members of their labs how hands-on their mentors are.</p>
<p>To paint with very broad strokes, tenured professors tend to have more money and be better-established in their fields, while pre-tenure professors tend to have less money and be more interested in upending the established order. But all of the professors at MIT are outstanding enough to have been offered jobs at MIT – as an undergrad, it’s not going to make a great deal of difference whether the lab you work in is super-famous or merely famous.</p>
<p>As a side note, please do not ask a professor during an interview whether you will be published if you do work in his/her lab. It would be reasonable to ask whether that professor has a policy of awarding authorship to undergrads, but do not ask whether you specifically will be published.</p>