ESB and ROTJ are pretty similar in that they were mixed while focusing on getting the main stereo right so that in the case of system failure the regular stereo would work fine. Thus the difference between 35 and 70 is largely that the latter was the more technically robust and discrete form whereas the 35mm had to be run through the matrixing process. They do have some differences that we know of, but this was mainly stuff like after premiere changes to ESB.
The mono mixes were made from scratch, and in the case of SW done later and thus have numerous tweaks, fixes and dialogue differentiations added to them. These mostly wound up in the 97 SE mix for both SW and ESB. I presume because GL and Burtt preferred them. Since I grew up with both the SE and OT, I tend to miss some of the SE effects and was so glad to hear that they were indeed original.
(Stuff like: the different Beru voice, Leia’s 44 magnum blaster, “Close the blast doors!”, “Blast it Wedge” etc.)
Try 'em all. See what you like. Personally I adore the monos, and only miss the stereo’s clarity. The monos are much more like classic Hollywood and action serials and the music is mixed differently too. Sometimes I wonder what one of our 70mm recreations would be like if we utilized the mono differences. Probably a lot like the 97 mixes, which apart from the new additions were quite faithful to the original 4 track masters and had great fidelity to them.