Hi guys.
I was admitted to Wharton / Lauder last year (LatAm, consulting) so maybe sharing a bit of my experience with the interview process can help someone out there. Assuming the process hasn't changed...interview was with an admission's officer.
Group dynamics: very hard to tell what really matters. I, for instance, made a huge dumb mistake during mine (literally said something that made no sense at the time, but quickly came back saying nevermind, it doesn't make sense, back to previous point) and it all worked out. I do think that you should try and "embody" a role play, be it the leader, the conciliator, the challenger, etc. Take a stance instead of being lost and going with the flow. Don't show off, it's not necessary. Be yourself on how you behave and push yourself to take a stance on the topic being discussed. In my group, "the leader" was admitted, the challenger wasn't and the conciliator was. That was not the case for other groups so...hard to tell.
Blind interview: DONT FORGET YOUR RESUME. Or you'll find yourself begging for the recepcionist to find a printer before you're called back to interview. It was literally 5 minutes and two questions: "do you think you were yourselve in the interview and why?" and "tell me anything you want me to know about you". So (i) good to be yourself so you can defend how you behaved in the group dynamics and (ii) I suggest you have a good elevator speech mixing your (QUICK) story recap with the 5-7 things you want to leave an impression on. It's really a monologue so it's good not to sound boring, pedantic, etc and also to flow a logic storyline. It's 5 minutes to make a (sticky!) good impression. Practicing may help. In my case, I spoke about my life trajectory and how it connects to my professional goals finishing with a "why" I thought Wharton was the place to go given everything.
Lauder was such an easygoing nice interview with a current student. We spoke about international experience, passions, a few classic "tell me a situation..." questions, but that was it. It was more of a conversation that anything else.
Hope that helps!
Cheers