6
I too like the Y. Sado/Vienna Tonkunstler Mahler recordings. I think they are by far the best sounding orchestral recordings ever to have been made in the Musikverein (most of the classic Decca recordings of the V.P.O. were done in the Sofiensaal). The orchestra plays many of the same indigenous Viennese instruments that the V.P.O. uses, so they sound a lot like them. Frankly, I think the Tonkunstler has the better percussion section, which is important for Mahler.
Sado's M1 very successfully integrates "Blumine" into the standard, revised version of the symphony, by taking the Scherzo a tad slower than usual (with lots of swing!), and the "Frere Jacques" in minor round a tad swifter than usual (third movement). I like both his M2 and M3 very much as well. I don't own either the M4 or M5. I wasn't crazy about the soprano on the M4, but it is a good reading. As John has already informed you, the M5 was recorded on tour in the Elbphilharmonie in Hamburg. For the M7, I was lucky enough to have friends who were vacationing in Vienna, so they picked up a copy of it for me at the Tonkunstler's ticket office in the downtown area (Herrengasse). The M6 will be coming out on CD's soon, but can be heard at Spotify and - I presume - Idagio. It is much better recorded than the much ballyhooed Bernstein/V.P.O. recording on DG. They will be performing M8 on the first weekend of June, so I will be very much looking forward to hearing that eventual recording.
Purely by coincidence, S. Bychkov/Czech Philharmonic are also doing M8 on the very same first weekend of June. I look forward to that recording as well.