Veneers and crowns are usually made of the same material. The difference is that veneers require less removal of tooth structure. I often combine both veneers and crowns in one case, or more often what we call "3/4 crowns" which is somewhere in between. It isn't a matter of which is better or worse--it really comes down to what you need for strength, function, and aesthetics. Come teeth may require veneers while other that take more force may need 3/4 crowns or full crowns. Discuss all with your dentist. The ceramist and dentist will also evaluate your bite and function to see what would work best for you.
Less tooth structure is removed during preparation for veneers as opposed to crowns. However, sometimes crowns are required if not enough tooth structure is available. Both options help improve one's smile, but an examination is needed to assess which treatment is suitable for you.