There really aren't many explanations except, "I like their voice", "They were so nice" and "They were fun." I can say the same thing about a lot of other CMs as well. Julian and Sam are great bartenders. Rui is a fantastic Head Server. Krasemir is a great server who is finally being recognized for his hard work by being promoted to Head Server. PJ is a really, really good Concierge Host. But I can also quantify what makes these CMs great. The CD thread doesn't really give that in the vast majority of the responses.
One person in that thread even acknowledges that everything is probably pretty much set by the corporate offices, so the CD just makes sure a plan is followed. I still don't fully understand why one CD matters over another. Perhaps it's just hard to put into words, as one of the posts in the other thread says.