Collagen and biotin both support healthy skin, nails, and hair. Collagen is a protein produced in the body, whereas biotin is a vitamin not found in the body. Foods or vitamin supplements are the only way to get biotin.  Each work to support healthy skin, nails, and hair. One is not necessarily better than the other. You can even take both supplements to stimulate the health of your hair. Always check with your doctor and follow their recommendations.