I much prefer the DTS DVD, which was mastered by Bob Vosgien, a true master (no pun intended) of his craft. He did a great job of smoothing out the differences between some of the tracks, in stark contrast to Craig Anderson, a DVD/BluRay author moonlighting as a mastering engineer who seems to have thrown a one-size-fits-all smiley face EQ on all of the Chicago albums (and all of the Doobie Bros. quads too).
If there are people who like the BluRay versions better I'm not going to try and dissuade them because we're incredibly lucky to have them at all, but I've probably listened to Chicago more than any other band in my life (though they don't get as much rotation these days as they did when I was younger) and the BluRay versions sound unlike any of the versions I grew up listening to, including the original quad and stereo vinyl releases and the original Columbia/Chicago Records CD masterings. As a result of Anderson's EQ choices, the horns are harsh and sibilant, and the bass is overpowering at times. The other unfortunate consequence of the boosted bottom and top end is that the midrange elements, vocals especially are recessed and sound almost buried in the mix at times, even if you're sitting exactly in the sweet spot. The only saving grace for me is that he seems to have gone pretty easy on the compression for the most part, though the bass drum does feel like it's had a little bit added to it as the percussive transients seem a lot more 'violent' than I've ever heard them before.
Sidenote, I have a spare copy of the Quadio CTA DVD (as well as a copy of the Aretha Greatest Hits DVD) if anyone wants to buy them - feel free to contact me via PM.