Personally I like trying the rides which are the same at both parks. Big Thunder is different enough from Disneyland that it's just a fun experience. Same with Peter Pan and Small World. If you have the time, the definitely try them. If you don't then skip those and go for the attractions DL does not have.
Philharmagic in Fantasyland is one of my favs! I really hope it makes it's way over to the west coast.