This one, I think.  In addition to the mono and 1993 mixes.

The only actual difference in content the 1985 version has from the 1977 stereo is that they added the C-3PO line about the tractor beam, which previously had only been in the mono mix.  Other than that there's no difference except for the stereo image reportedly being wider and a possible increase in fidelity due to the remastering.

I grew up with the 1985 mix on vhs, so going back to the original is just how I remember it aside from that one line.  The 70mm is also very familiar, because while it has much greater dynamic range and bass presence, there are only a few minor changes in sound effects from the stereo mix.

The 1997 version does not come from any previous mix directly, but it's clear that the original tracks were used for most of it, because it still has that familiar sound of Star Wars in stereo for the parts that aren't changed significantly.  However, it generally doesn't come off as well as the 70mm version, because its dynamic range is usually somewhat lower, and its EQ tends towards emphasis of the high frequencies, which makes it sound a bit tinny and sometimes exposes noise in the source elements that was previously better masked.  (That's probably why they wanted to remix again in 2004, but we all know how horribly that turned out.)