RtW, although the same as Mother's, has been re-encoded, resized, color enhanced and then pulleddown to 29.97 fps.
Moth3r's is a more raw version of the same video with more lines of resolution. Much better for editing. OCP will need to re-encode those frames and probably apply a different color balance when he uses them.
It's just better to go to the source... assuming I even do a RtW RotJ. Between Classic Edition and Citizen, I'm not sure it's needed. Not to say it might not be done for completeness sake.