For cosmetic reasons, are veneers or crowns better? About eight of my teeth, top and bottom

Excellent question. 
It depends on the individual situation. Typically, veneers are more conservative and thus you preserve a lot of your own natural tooth structure; however, for individuals who are grinders, and have worn down teeth or an unusual bite/occlusion, crowns would be the better alternative. In most cases though, we can achieve great aesthetics with porcelain veneers. 
The best way to go is to schedule an in-person exam with a cosmetic dentist that is experienced in both crowns and veneers. 
Best of luck!
Dr. Neil Hadaegh
#beverlyhillsdentist
#cosmeticdentist 

Hi:Veneers require less of the tooth structure to be shaved down, however there are circumstances that a crown is required for better protection.Best,Dr. Maddahi

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.

Porcelain veneers and porcelain crowns are very similar in appearance (and often made from the exact same material), but a veneer removes less enamel than a crown.  This is a good idea, if possible, in case more work is needed in the future.  If very little tooth structure remains and a crown needs to be replaced, a replacement may not be an option.  If a tooth already has a crown, then a veneer is no longer possible.