As a former Norwell High School teacher, albeit chemistry, I would hope our students would recognize the grammatical error in "more superior". Sorry, I could not resist the dig. ( For those unfamiliar, Deborah is from Marshfield, a town adjoining Norwell, Massachusetts).
First, there is no such commercially available strength as 0.5 in either product. If you were to compare each in its cream form at say, 0.05 % concentration, which is found in both Tazorac and Retin A, I would say that Tazorac is the stronger of the two. However, we do not have an accurate assay for Retinoids as we do for steroids, this is only a general impression. Maybe, we are substutuing "stronger" for more irritating, assuming that something that is irritating, by nature, is stronger. Bottom line, though, is I usually recommend Tazorac over Tretinoin when patients ask me advice on how to keep their skin youthful.
When comparing the two, please realize that gels are stronger than creams. This is because they are more occlusive, penetrate the skin better, and its occlusive base also decreases its loss from the skin.
Tazorac, actually both compounds, but especially Tazorac, takes some getting used to. It is often best to start with a lower strength ( 0.05) and work up to the stronger (.1). This may require a moisturizer. You can use the moisturizer either before or after application. ( A recent study found that it made no difference).I find that Cerave AM or PM are quite compatible with Tazorac. Since Tazorac is applied at night, the PM is a good choice. Cerave PM also contains some healthy ingredients for the skin in its ceramindes, hyaluronic acid and niacinamide.
Be sure that your skin is dry with either medication. Application should be at night since the sun will wreak havoc on the retinoid molecule, besides perhaps giving you a slight sunburn.
Both should not be used during pregnancy but Tazorac especially so, since it carries a Category X.