I don't see any long term benefits from hitting GCA. Our landings are to be a quick hit-and-run operation. We have to hit hard; as hard as we can, trying to do permanent damage. Just razing some undeveloped towns isn't going to hurt them as much as is needed. Destroy their FP, Leo's, Pyramids or any other Wonder, or at least try to do so with all our force. If we can accomplish that: Permanent damage. If we can't accomplish that we have forced them to keep more and more units as a protective force. Pshycological advantage: From then on simply sending an empty fleet of 8 caravels somewhere later in the game will ignite a new panic-reaction. Even more if we coordinate that with Poly.