I'm going to go with 16 as the best. Yeah, it was easy, but that was kind of the point - they were expecting a big complex mental task, and it threw them for a loop when it wasn't even a task on its own but rather the second part of another task.
12's was good, as was 17's, but they both have big flaws - 17 using two random people as decoy greeters instead of picking two more hat-wearing former greeters, and 12 being easier than it looked. Solving it with logic alone, some of the clues/rules aren't even needed, and watching it as a fan of logic puzzles it just looked clumsy.