I'm going to throw another curve. In a big, complete set like this, I think it helps to use recordings that have tons of extra tracks. For that reason alone, I would have chosen the Kaplan/VPO M2 (it's far better than most people think); the Abbado/VPO M3, and the Abbado/CSO M7. All of those came with tons of extra tracks.
The Abbado/VPO M3 doesn't have great sound. But by this point, surely DG could re-phase and re-master it to the point where it could actually sound quite good. It also possesses the incomparable Jessye Norman.
I know there are people who would squake about using the Kaplan/VPO M2. But it's actually a very good performance - not a great mezzo, I know - and it has a pretty full sounding organ. That's important
Therefore, my lineup would look something like this:
M1: Ozawa/BSO, with "Blumine" placed in the 2nd movement position (not just an addendum).
M2: Kaplan/VPO (with tons of extra tracks)
M3: Abbado/VPO (w/ tons of extra tracks)
M4: Chailly/Concertgebouw (B. Bonney is great)
M5: Kubelik/BRSO
M6: Boulez/VPO (still his best Mahler performance)
M6: Abbado/BPO (for A/S movement order)
M7: Abbado/CSO (for the tons of extra tracks)
M8: Sinopoli/Philharmonia
DLvdE: Giulini/BPO (I like their pick on this one)
M9: Karajan/BPO (again, the "live" one for all the extra tracks)
M10: Harding/VPO (but the Chailly is just as great; maybe even better)
So yes, I would give two M6 performances; one in S/A, and the other in A/S. Besides, DG is stacked full of good M6 recordings.
I would also use the Chailly "DKW", instead of the truly dull Abbado/BPO one. Either that, or wait and see just how good this Boulez/Cleveland one turns out.
Just my two cents. I think they could have thought this through a bit more.
