The thing about the 1993 mixes is that for the most part they sound quite a bit better than the 35mm stereo versions, because they were made specifically with the goal of obtaining a powerful sound with unrestricted dynamic range, which they were able to achieve with digital PCM tracks on laserdisc but hadn't been possible in stereo before, due to the technical limitations of 35mm optical sound. (All three films were made before the advent of Dolby SR, which increased the dynamic potential of analog 35mm sound by 3 decibels, though that still isn't as much increase as the '93 versions provide.) Because of this pronounced dynamic superiority, I find them preferable in the overall quality of sound.
It is unfortunate that for Star Wars they could not leave well enough alone, deeming it unfathomably 'necessary' to add a bunch of extra sound effects on top of the existing 70mm transfer that was used. Those awful, obnoxiously loud shattering glass sounds in particular really scream out "see, isn't this new improved remix so much better?" It's telling that many of the same '93 additions also found their way into the special edition a few years later, along with many equally pointless new sounds. One of the reasons I made the 70mm recreation was to be able to hear the film with all its dynamic power intact but with the extraneous sounds removed, along with restoring the LFE punch that had been missing since its original release. I'm not knocking the 35's though; despite being limited they still sound good, and have the benefit of being entirely authentic. ;)
Empire and Jedi fare better in the 1993 versions, since no extra sound effects were added. Unlike Star Wars, though, they were not derived from their respective 70mm mixes--Empire came from an unlimited 4-track master conforming to the 35mm edit, and Jedi was more thoroughly remixed from the multi-track stems. The fact that the snowspeeder crash sound in Empire is missing simply means that it was probably a last minute addition to the 35mm mix, and was not present in the earlier generation source used for the '93. From that assumption, I believe it was probably missing from the 70mm mix also, though there's no way to be sure. For what it's worth I'm probably going to put the snowspeeder sound into the 5.1, though I haven't decided whether to use the 35mm version or get the individual sound effect from the special edition.
In addition to individual preference, which mixes will sound best really depends what kind of audio equipment is being used. If it is something without a lot of amplifier power, the dynamically limited 35mm mixes would be ideal, because they can be played without danger of peak distortion. They are also suited to situations where very high volumes are not desirable. For more capable stereo setups, the '93 mixes (and in that I include the stereo 70mm, since it is the '93 without the extra sounds) will provide greater satisfaction. People with full home theatre setups will naturally want to select the 5.1 mixes, which in spirit (if not always in precise detail) come about as close to the power and overall feel of the 70mm theatrical releases as can be done with the source materials available.
If you like, I reckon I could write a description of this stuff (detailed yet concise) so that it could be included with the dvd's, to help minimise confusion about the audio for anyone who obtains them.