I haven't been involved in a, 'what are your favorites' type poll in a long time. I'll make a few comments based one what I see here.
I think the Klemperer live recording with the Vienna Phil. is superior to the Philharmonia studio one. It's been on various Italian 'pirates', but also got issued in a Klemperer box by Testament. I just today heard a rumor that a tape exists for Klemperer's last M9 performance, live, with the New Philharmonia.
I also have a preference for Karajan's studio recording over his live one, but not by much. Both are very good in my book.
I like the 'pirate' of Bernstein's BSO (Tangelwood) performance the best, which means I like it the best of any. The Israel Phil. one on Helicon comes in second for me, followed by his earlier N.Y. Phil. recording. The Concertgebouw one comes in last place for me. For the Concertgebouw, I like Chailly's best. The Bernstein estate should really make Lenny's BSO M9 official.
I do share enthusiasm for Sinopoli's Dresden M9. I wish there was more Mahler with the Staatskapelle in general. Perhaps the recent Thielemann/Dresden M3 will get issued in some format.
I do not, however, have strong feelings for the Giulini/CSO M9. The two outer movements have spectacular moments - very expressionistic. However, the two inner movements are too heavy and just misfire. The performance just doesn't 'hang' for me. There exists a pirate of Giulini doing M9 in Los Angeles, and I'm willing to bet that it's actually better (but maybe not).
Speaking of L.A., I think the Dudamel M9 is surprisingly good and mature sounding. It has received much customer praise at Amazon, with very few detractors. I like it for Dudamel's pacing, and for the gorgeous playing of the L.A. Phil. I'm hoping that DG hasn't abandoned plans to issue a Dudamel/LAPO M6.
My favorite single disc version of M9 is the new Daniel Harding/Swedish R.S.O on Harmonia Mundi. The pacing is superb.
For Haitink, I think his BRSO one is best (also a single disc).
I like Solti's earlier LSO M9 in the first three movements, but less so in the finale. It's definitely better than his CSO remake, which struck me as a Karajan clone.
We're lucky, because pretty much every conductor and orchestra seems to 'rise to the occasion' when it comes to Mahler 9.
Barry