I also think the 70mm mix is the best version sonically. In terms of content, though, I think the mono mix would be the definitive version - it’s the mix that had the most effort put into it since most theaters at the time were only equipped for mono, and that would be the mix most people would hear (kind of like how the Beatles put the most effort into the mono mixes of their albums for the same reason). Ben Burtt himself even considered it the definitive mix until SW came out on home video and the “inferior” stereo mix became the standard version…
Now that last part about Burtt considering it the definitive mix is particularly interesting. I always forget what the main differences between the mono and stereo versions usually are. I know the siren aboard the Tantive IV in the beginning is different, but that’s about it.