Its been a few years since I played them as well. I would agree the East is the better course, although they're pretty similar and both courses are good. The East has the famous double dogleg par-5 over the ponds, which sometimes is given as an example of RTJ's heroic ideal. On both courses the best holes are the holes near the sea. From what I understand originally all the ocean holes were part of one golf course, and then RTJ came back a few years later and expanded it to create two golf courses. That original course must have been a pretty damn good.
I don't know about any other courses on the island...Casa de Campo is only short plain trip away.