As of right now I don’t plan on tracking down the Definitive Collection or the THX (Faces) Editions because it seems redundant. I already own the 2-Disc DVD Editions of The Star Wars Trilogy from September of 2006 and the Letterboxed DVDs of the Original Versions included in those sets were sourced from the same Video Masters used for those specific LaserDisc Editions.
There is merit in having both the DC or Faces and the GOUT. The GOUT has much better video quality, but the LDs have much better audio quality.
I’ve seen comparisons and yes the 2006 Letterboxed DVDs do look noticeably super to the Definitive Collection and the THX (Faces) Editions. But yes the audio on the LaserDiscs is superior because they use PCM Stereo which is lossless whereas the DVDs uses Dolby 2.0 Surround which is lossy.
Maybe in the near future I’ll change my mind and track down either the Definitive Collection or the THX (Faces) Editions but as of right now I’m okay without them.