Medieval

Should old art, old buildings, be removed or torn down to make way for the new? For example, the Chicago Stock Exchange building  in a prime downtown location was designed by the great architect Louis Sullivan, called "the father of modernism." A major civic argument broke out when the property was purchased by developers who wanted to demolish the Stock Exchange and replace it with an undistinguished office building. The developers won. The trading room of the Stock Exchange was dismantled and rebuilt in a wing of the Art Institute of Chicago.  For Sullivan: http://www.answers.com/topic/louis-sullivan

So: What would the arguments be for preserving, or for tearing down and replacing?