I read the great news yesterday that doctors at one of our local hospital are offering Tai Chi to their patients for coping with chronic pain. This is good news. But don't be deceived by the term "medical Tai Chi". Just because a doctor with some Tai Chi training is teaching a high quality of Tai Chi, doesn't mean that all other kinds are useless 'only exercise' done by people in the park. That's a very broad and unfounded assumption.
The truth is; that done properly, following all the principles of good Tai Chi:
proper alignment, breathing, mental focus, muscle relaxation, any Tai Chi has the potential to be so called 'medical Tai Chi". In other words, if you do your moves properly - you will get the health benefits.
This is also the reason why I do not recommend Tai Chi DVD's - it is limited in the expert guidance a live teacher can impart.