The first one is the one that I grew up with - it's the 1991 or 1992 box set. It uses the 1985 audio mix, and is pre-THX, so it's from the same master as the Japanese Special Collection (if I'm not mistaken on that). I love the VHS sleeves for those, as well - I've even made DVD covers based on the design.
The second one is the 1995 "Faces" set, the last time the originals were released until the 2006 DVDs. They use the same master as the 1993 Definitive Collection/1995 "Faces" LDs, and the 2006 DVDs (though, since it's fullscreen, it's possible that a different master was used, I'm not 100% sure on that). It uses the 1993 audio mix.
The "Faces" set has a bunch of DNR (digital noise reduction) applied, which makes it smear pretty bad in motion scenes. The earlier one doesn't have this, but detail isn't quite as good in non-motion scenes.
Note that neither one of those contains the "true original" version of Star Wars - they both use the 1981 "Episode IV: A New Hope" crawl, as did all home video releases pre-2006. The earlier ones' audio mixes are more true to the theatrical mixes than the "Faces" set, but they're still not quite the same. (At least for Star Wars and possibly Empire - not sure about Jedi's audio mixes, and no one around here seems to be.)