How about thinking about "Core Stability" and then look at what the different methods offer?
Or "Body awareness" thro.....
Or postural improvement through "Proprioception" (because I think Alexander is really good for that and I don't know the others myself so well
Or patient/client compliance in the 3 methods outside class time.
Or something about chronic back pain sufferers who have found relief thro one of the three methods and WHY ?? Ha! enough for years of research
have fun!