I think this is where I -- and possibly Wudang, although I am somewhat loathe to speak for him -- differ with you.
I do not consider "the Yang short form" to be "much better," nor do I consider the eight pieces to be a valuable "meditation/breathing" exercise. If all you want is "focus, decreasing stress & general posture," then a walk in the part or a decent set of football stretches will do you that for you. Or, for that matter, improvising slow range-of-motion exercises as TBK suggests.
The people in the park who are waving their hands like fat Westerners usually aren't doing themselves much good either.
Tai chi is an extremely effective and useful martial art when taught properly. As I believe I mentioned upthread, I know of something like four instructors, world-wide, that know how to use tai chi as a martial art (and that teach it) and that can get the sort of health benefits that one would expect of a genuine martial art system out of it. (I was privileged to study, briefly, under one of them.)
The people waving their hands in the park are wasting time and money.