A mural, regardless of where it is painted, is designed and created with a bend towards ambience.  It isn't necessarily lacking in detail so much as it is designed to be viewed from a distance and is therefore less refined in its details.  The process yields a finished product more quickly than a fine art piece, allowing for a better price in most cases.  A client can, however, request more attention to detail, but is then stepping into a fine art commission category.