There is no question that Anderson is the better prospect. But if he can be used in a deal for, say Zambrano or Cabrera, AND the Sox felt that Bates had some major league potential, I could see using Anderson. The fact is that they will not co-exist on the Red Sox, so at Anderson's age and with the time it will take between now and when he is on the Sox, the Sox would have the time to compensate for a loss of a prospect of his caliber (gaining, of course, something significant by trading him) through FA or draft or Bates.
I understand how phenomenal Anderson is, however, and understand anyone's hesitance at even discussing moving him.