At Wharton, all interviews are equal. There is no advantage or disadvantage to interviewing with staff versus interviewing on campus.
Most questions are common interview questions. Topics include: your reasons for wanting an MBA, your reasons for choosing Wharton (and why Wharton should choose you), your career goals, your spare time, your values and morals, etc.
Interviewers are typically “blind”, meaning that they have not seen your application. Blind interviews reduce biases and pre-judgments.
Finally, avoid pre-rehearsed speeches and take your queues from the interviewer. You’ll be much better off.