I have not seen much in the way of research regarding other bathing products, though. This recently published open access article in Energy Procedia titled The Inherent Biodegradability Characteritics of Light Greywater for the Different Bathe Products by Chinese researchers He Weitaoa, Wang Yayia, Yang Jiana, Zhao Xub explores this issue on bath soaps and shampoos. The sources of their research are the mainstream products that frequently show up on TV advertisements.
There was little difference in biodegradation between the bathe products...[and]...It revealed that all of the products met the requirements of environmentally friendly products.
Maybe it does not cost extra to save the environment after all.