I'd say ANH or ESB are the easiest. The armor is the same, helmet paint schemes, blaster and holster are different. ROTJ armor is different than ANH and ESB, as is the helmet.
GML = Garrison Membership Liaison -----
Shimming is where you add plastic between two pieces to bridge a gap where there would otherwise be no plastic. For example, if the ab and back plate do not meet on the sides of your body and there is a gap, you can add plastic between the two pieces to bridge the gap so no black undersuit shows. Terry has a great writeup here that includes some info on shims----