http://www.therpf.com/f67/darth-vader-costume-displays-anh-esb-rotj-151798/
Just came across these. ^^ Most impressive. For me, aside from the cape difference and the shiny/matte helmet I've aways had a tough time telling the difference between Vader's costume in the trilogy.
I used to be bothered by Vader looking a little rough in ANH and by his cape covering his upper breast plate. (I even made a comparison pic to show the difference which I've seen floating around on this forum) Now I don't mind - it is what it is. That said, I still wouldn't mind seeing a short proof of concept of a shiny helmet esbish looking Vader in AnH just for fun. :)
On a related note, GL really should have shown Vader looking more like his ANH version rather than the latter version.