In order to be considered a "pharma grade" product, the FDA requires the active ingredients to be 99.9% pure. Additionally, there needs to be scientific evidence that the product is beneficial and does what it is advertised to do. the efficacy of the product is substantially better. They are made to not "sit on the skin" but are formulated to penetrate to the deeper layers where they can be most effective. Medical grade products are subject by the FDA to rigorous and extensive testing and clinical studies. Over the counter products are not held to such a high standard, in fact some do not require any studies or research backing their formulation.
The potency of the ingredients are far superior.
Because the ingredients are more concentrated, the amount necessary to achieve the results is less. Basically, you need to use less product to achieve maximum results.
Because the quality of the ingredients is regulated, there are fewer sensitivities and adverse reactions.
Many pharma grade product companies do not test on animals (environmentally sensitive)
Less synthetic ingredients, less chemicals being absorbed into body.