What’s the Public Benefit of Silverstein’s Trade Center Towers?

Once again, the rebuilding of the World Trade Center is caught in a public fight. 
Developer Larry Silverstein and the Port Authority are sparring over a renegotiation of a development agreement for the site, as the economic crisis and lending drought have rendered impossible the existing timetable, which called for the three towers to be privately financed and built by 2014. The debate has flared in public and through the media, and if the Port Authority (which owns the site) and Mr. Silverstein (who plans to develop all three towers) fail to find common ground, the entire site could face further delays.

What’s the Public Benefit of Silverstein’s Trade Center Towers?