Re: Mya QT and Mya QT s-class
I think they're just different in stem height. I actually had to look up S-Class, because I've never heard the Mya QTs sub-grouped. I've only seen them sold with the height listed. Some are 12", 13" and 14". The S-Class, I believe, is the tallest Mya QT which would be the one I'd go with.
But I'd recommend reading and watching some of the hookah reviews here to get an idea as to how they smoke. There are quite a few Mya QT reviews on here and the video ones show that the Mya QT smokes pretty darn well for such a small hookah.