Better, superior, preferable mean more worthy or more pleasing than another or others.
Better, which often serves as the comparative of good, in this sense implies a quality or character in a person or thing that surpasses or exceeds that in the one or ones called good.
Often, however, better is used in comparison or contrast with something that can be described as bad or with something that may be good, bad, or indifferent yet from the point of view of the speaker or writer is to be rejected as totally undesirable in comparison.
Superior in all its uses retains some feeling of its basic meaning, higher in physical position, which is now largely restricted to technical contexts in which it implies opposition to what is below (inferior); thus, the upper jaw or maxilla is sometimes distinguished as the superior maxilla from the lower jaw or mandible which is then designated the inferior maxilla.
Superior often implies a scale (as of values or ranks) and emphasizes height (as of status, quality, or worth); thus, if a student is doing good work one might suggest that he could do better (as compared with his previous accomplishment) if he tried, and might hope that his added efforts would produce a truly superior result (as compared either with any relevant accomplishment or with a scale of possible accomplishments); one might like an author’s new book better than his last but rate it superior to anything he had previously written.
Preferable implies a choice between two things or one thing and all others usually on the ground that the thing chosen is better by comparison or is superior in quality, status, or kind. But its chief emphasis is upon relative desirability, and the other implications may be greatly obscured or lost upon occasion.