I am simply restating arguments that have been made in the past:
On campus and off campus interviews are evaluated equally. The main argument for doing an on-campus interview is that the 2nd years on-campus have likely given dozens of interviews and have a "normalized" perception of you, because they have enough to compare you to. Additionally, those 2nd years go through extensive training on how to evaluate candidates. Some people fear that alums can be too risky, because an alum may only interview one or two candidates, and that may result in a skewed evaluation.
All of that said, my opinion is that at the end of the day, you can have a bad connection with an alum, but similarly you can have a bad connection with a 2nd year on campus. You really don't have control over anything except how prepared you are and how well you conduct yourself in the interview. When thinking about all of these statistics/stereotypes/arguments, you have to remember that at the end of the day, you are only one person in the sample size and anything can happen. You can try to (over)analyze but you really cannot do anything to force a connection with an interviewer. So do your best to resist overanalyzing and interview wherever is convenient and most comfortable for you.
As far as interviewing goes, Booth is not out to trick you during your interviews. The questions asked are very standard and it is a very comfortable interviewing process. Prepare well, and it will go smoothly.
Also to address the GMAT 'Awaiting' questions, I've said it before and I'll say it again, mine said 'Awaiting' until Booth conducted the employment verification in August (yes, just a couple weeks before orientation). So please, do not worry about that red X, it is meaningless. As long as you submitted your official scores to Booth, you are fine.