Well, I splurged for the Tilson-Thomas set on SFS Media. Should be here in a few weeks (back-ordered on Amazon but got it at a good price). I'll be sure to report out. I have a feeling that when the Minnesota/Vanska completes their Mahler cycle (they still have 3, 8, and 9 to record), it will be offered as a package and I'll def pick that one up, because BIS just seems to be incapable of making anything but a superlative recording.
I love Mahler. I've been to Mahler Fests in Berlin and Amsterdam, and have seen the 8th live nine times in my life (including in LA/Dudamel in May 2019, which blew me away). I'm not a musicologist, so I can't analyze details about how one orchestra plays versus another (except for tempos). Any major orchestra that's been recorded will do a yeoman's job, at least. So, in the end, I try to listen to recordings that are well-recorded. My system (Bryston amp/preamp, Meridian 508.24 CD player, Thiel CS 2.4 speakers) is fairly revealing, and I'm unwilling anymore to listen to shrill, muffled, noisy recordings. I avoid historical recordings because I hate mono and they're usually filled with noise.