Butter or margarine- which do you think is worse? why?

I don't feel that "natural" or "unnatural" are useful terms in discussing food. Asbestos is sourced in nature, as are bee and rattlesnake venom, but we don't imagine that they are necessarily safer than any man-made substance. That said, I think that butter is the least evil of spreadable fat products. I have no science to back that up, it's just what tastes best to me. I don't use butter at home. Olive oil is just as suitable for scrambling eggs and spreading on bread.