Its a bit thicker, its white, it has no headphone jack, the door lock is gone, the AV port has moved from the side to the back...all of these differences are pretty much meaningless when compared to the fact that original Duos seem to pretty much all have leaking capacitors at this point, and Duo Rs for some reason don't. If you can find a "re-capped" original Duo, that would be OK, but I wouldn't get one unless its been overhauled.
On a side note, remember when a system had to have a headphone jack to be taken seriously? Man, those were the days...