You are asking whether the alpha-hydroxy acid, Glycolic acid, or the beta hydroxy acid, salicylic acid is superior. In this case I am going to have to go with the Beta dog, sal acid.
A study published in Dermatologic Surgery last year compared the two types of peels and gave the nod to the salicylic acid peel. This study, performed by dermatologists at the St. Louis University confirmed the impression that most dermatologists have had for years: that the Beta peel is preferred for acne and the glycolic peel for skin lightening and rejuvenation.
The results of the Beta hydroxy acid peel (BHA) lasted a bit longer and had fewer side effects such as irritation. Both peels were effective in reducing acne lesions, however.
This was the only study I am aware of that compared these two peels.
Usually the beneficial effect of the peels occurred in about two weeks.
