More should be dropped from this wordy expression; preferable means "more desirable." Say "This apartment is preferable (not more preferable) to that one." (Notice that to is used in the preceding sentence; never say "prefer than.") The comparative degree of adjectives and adverbs expresses the idea of more (or less): better (not more better); sicker (not more sicker); slower (not more slower); faster (not less, or more, faster).
Dictionary of problem words and expressions. Harry Shaw. 1975.