There are quite a few differences between the ESB and RotJ Vader. All armor parts are cleaned up more and don't have the leftover paint damage and scratches left over from the ANH parts that are seen on the ESB stuff. There are a few instances in RotJ where they use ESB parts and they are instantly recognizable to people who study the props and the differences. And they used a few shots of Vader from ESB as well.
Besides sanding down the bumps and scratches to a more smooth finish they also made some distinct alterations.
On the ESB dome at the widows peak area they had rounded the bottom tip a lot and sanded the area with the Y crease so it is barely visible, whereas on the RotJ they sanded the bottom flat and filled the Y crease area completely.
The mask is basically the same as ESB, only slimmer, again sanded more, and painted differently. The "larger eyes" look is caused by the dome sitting higher and the front of the eyebrow surface has been painted black halfway up the surface, making it appear slimmer and the eyes "larger". The one with the fatter bottom lip is a stunt fencing helmet with perspex cheeks and chin - Seen predominantly at the end duel and when Vader watches Luke being tortured. They also cut the chin triangle larger and more pointy than ESB.
They also had the shoulder bells sit level with the armor and not beneath it like ANH and ESB.
The chest box is more simplified than ESB - more straight. Where the rods and various greeblies on the ESB were all different, the RotJ goes for a more mirrored look with the rods and metal greeblies and removed two of the smaller greeblies from the box. Unsure of the belt boxes - haven't studied them as much yet, but they seem fairly similar to the ESB boxes, but perhaps with different colored green lens covers (even two different colored green lens covers on each box).
Because of the smoother look to the parts, having been sanded, the shine seems more gloss than ESB, but they were painted with the same colors and finished the same. Paint scheme on the mask is slightly different between the two. The lighting causes a lot of how different the two look, but the props are actually pretty similar.
