This is a recent study by Cramer et al. (2016) that compared whether different yoga styles varied in their positive results reported by the participants. Cramer et al. reviewed and analysed the results of 306 randomised control trials (RCTs).
“As previously reported, more than 90% of all 306 published RCTs on yoga reached positive conclusions.8 This secondary analysis found that the proportion of positive, neutral or negative conclu- sions was independent of the applied yoga style. This might be interpreted as demonstrating that the efficacy of yoga does not depend on the specific yoga style that was used but that all (or most) yoga styles can be regarded as equally effective. However, it should be noted that most yoga styles were applied in only a few randomised control trials (RCTs). Only 5 out of 52 yoga styles, or categories of yoga style, were used in more than 10 RCTs. Thus, the findings of this review might be applicable mainly to the most commonly applied yoga styles: hatha yoga, Iyengar yoga, the integrated approach to yoga therapy and pranayama.
While there were no significant differences between different yoga styles, RCTs that compared yoga to an untreated control group were more likely to reach positive conclusions than those RCTs without untreated control groups. I.e., Randomised control trials that compared yoga to no treatment were more often positive than those that compared yoga to other active treatments. This is in line with meta-analyses suggesting that while yoga might be more effective than no treat-ment, it is commonly not superior to an active comparator.”
Cramer, H., Lauche, R., Langhorst, J., & Dobos, G. (2016). Is one yoga style better than another? A systematic review of associations of yoga style and conclusions in randomized yoga trials. Complementary Therapies in Medicine. Vol. 25. http://dx.doi.org/10.1016/j.ctim.2016.02.015