I prefer A/S, but I just don't feel that it's nearly as important an issue as that of tempo. It's interesting to note that the estimated timings that are printed on the conductor's score indicate 14 minutes for the andante movement, and 11 for the scherzo. That's pretty fast, especially the scherzo. I presume that those estimates came from Mahler himself, but perhaps not. Anyway, at least Schwarz didn't drag the two inner movements, as so many conductors do these days.
I still contend that some recorded performances work better in A/S, while others work better in S/A. I feel that the MTT/SFSO M6 definitely works better when switched into A/S order. As a matter of fact, MTT now performs it that way. I also feel that the Karajan M6 works better when played back A/S. Conversely, I like Abbado's Berlin M6 better when it's switched to S/A order, greatly because the end of his first movement is nearly identical to the start of his scherzo, in terms of tempo. Anyway, you get the idea. To me, it's still very much a finale driven symphony.
Barry