Is L-ascorbic acid better than vitamin C derivatives like ascorbyl glucoside or THD ascorbate?

L-ascorbic acid (LAA) has the deepest research base for brightening and antioxidant defense, but it is unstable, can sting, and oxidizes quickly once opened. Derivatives like ascorbyl glucoside, sodium ascorbyl phosphate, and tetrahexyldecyl (THD) ascorbate are more stable and gentler, but typically work more slowly and produce subtler results. Sensitive-skin reviewers across specialist subreddits generally prefer derivatives; people chasing visible hyperpigmentation results tend to gravitate to 10–20% LAA formulas.