I have been wondering this same bit for a long time. Can anyone help us? I'm sure there are more than just myself and mmgraphics that would like to know.
Well the dents are more defined in the ESB version, especially on the right shoulder. The dents are all in the same locations, just sharper on ESB. However the dent on the right shoulder on ESB is a lot more detailed when compared to ROTJ.
Well the armours are painted different schemes which I assume you all ready know. Other than that the armour is basically interchangeable (such as BobaMaker Parts), or you could go a specific movie version based on the sharpness, shape, and depth of the dents (FettPride).