Here's a recap of the two different mixes using info taken here and there.
I assume there are only two mixes for T2, and no further remix was made after the UE remix?
Terminator 2 soundtracks history
1991 - CDS MIX
T2 - original Artisan DVD uses as sound master for the 5.1 Dolby Digital soundtrack the unlimited mix created for the Cinema Digital Sound prints. No other DVD or Blu-ray has used the CDS mix. The CDS mix has a more "quadraphonic" soundfield to it with lots of side-wall phantom imaging. You can hear the dramatic difference in the first few minutes of the film. The CDS mix is the best both in overall fidelity and in the amazing sound imaging - its almost holographic.
The first T2 DVD of the theatrical cut from Artisan uses the same 5.1 channel mix that was prepared for the 70mm Kodak/ORC Cinema Digital Sound prints. Although T2 was also release in 6-track mag 70mm, the CDS 5.1 mix was completely unlimited in dynamics and had deeper bass since 70mm mag can't go lower than about 30 Hz in the bass and can only have peaks about 16db or so above reference level.
The CDS mix had peaks +20db above reference and bass to below 20 Hz. Because CDS was basically brand new, the CDS mix for T2 was prepared separately from the 70mm 6-track mag version to take advantage of the CDS system.
For the DVD, Artisan used the CDS 5.1 digital master, which had been archived on the S-VHS ADAT format. CDS was a lossless 44.1kHz sampling, 16-bit system that used a modified form of Delta Modulation to pack the audio into a total bitrate of just over 5mbp/s.
Ultimate DVD remix
After locating all the materials of the film for Artisan Ultimate T2 DVD, Van brought in Gary Rydstrom, the movie's original sound designer and the re-recording mixer who had won two of his four Oscars for T2, to begin re-mixing the entire movie and adjust it to near-field listening environments. "We did the mix last November," Van recalls. He and Lightstorm representatives went to George Lucas' Skywalker Ranch to remix the movie's soundtrack for use on the DVD. It took them about a week to do the work needed for both versions of the film and several other elements for the disc. "Luckily in 1993 when we did the Special Edition Laserdisc, we tried to do all the audio materials in six track, which helped us immensely now."
The soundtrack for the previous DVD release of T2 was created using a Sony linear 6-track, but for this release, Van and Gary went back to the original source elements they found. The result is a brand new 5.1 Dolby Digital mix that even contains spatial information for an additional rear center speaker as outlined in the Dolby Surround EX specifications. "The disc will actually contain the Dolby Digital 5.1 plus-EX track and a Dolby Digital 2.0 mix".