I'm pretty much exactly the opposite of Meows post...we've actually discussed this before too😉
So IMO, Traditional interview>>>>MMI ABSOLUTELY
I feel your true personality is more accurately portrayed when you spend a longer time with a single interviewer/panel of interviewers in a traditional set-up. You are able to actually establish a "real life" type of conversation rather than a forced standardized answer. If personality is what that are trying to gauge, I fail to see how the MMI is superior. I also feel as though my true self is better revealed when talking about my story/things that interest me vs. ridiculous open ended questions/bogus "what would you do" scenarios. Like someone mentioned before, it is easier to "act" your way through these types of scenarios for short bursts of time as exists in an MMI and I am sure many people do it. It really isn't hard to gauge what theme they are testing/looking for at each station.
That said, I didn't hate the MMI. If the one that I participated in (ironically at the school I'll be attending) didnt have a double long traditional interview station built into it, I probably would have cared even less for it. I do see the benefits for some folks who like the fact that they can basically start fresh after each station, and that if they don't vibe well with one interviewer their whole interview isn't compromised because of it...still, I just don't think it really promotes an honest reflection of one's self and can be easily faked.