I have been slowly getting to grips with two cycles on Blu-ray over the last couple of years.
and
Although I've watched a few of them on the big telly + mid-fi stereo in the living room, I have enjoyed them much more just listening on the main hifi without visuals. This has been achieved courtesy of two 30-day trial pieces of software, MakeMKV and DVD Audio Extractor which used together allow the stereo PCM soundtracks to be ripped to FLAC files, which are now on my music server. The Abbado/Lucerne set is in excellent 48/24 sound, while the Concertgebouw set is in stunning 96/24.
I do think Mahler is generally best served by good recordings and good equipment - the incredible orchestration, huge dynamic range and ever-changing tonal colours and timbres deserve hifi.... I'm convinced that Mahler could never have become the popular composer he is now without the invention of stereo hifi, and I think the fact that Mahler's music was generally not discovered by classical fans at large until the 1960s and onwards bears this out.
Abbado's Lucerne Festival performances are rightly renowned, the only let down is that the sound on the 2nd is a bit flat by comparison to the others. But not too bothered as the 2nd has a strange effect on me: about 5 mins in to the finale, I start wondering when this nonsense will ever end! The 9th is available on a separate disc, and its well worth having, maybe one of the greatest performances. I don't think Abbado recorded the 8th at Lucerne - again, not too bothered, its my least favourite Mahler.
The set includes bonuses of Prokofiev's 3rd concerto with Yuja Wang, and Magdalena Kozena singing the Ruckert Lieder, another good one, really spine tingling in "Ich bin der Welt abhanden gekommen".
The Concertgebouw set, recorded between 2010-2012, is a much more mixed bag. Basically, with Mariss Jansons on the podium with his orchestra, the performances are wonderful. He takes charge for 2, 3 and 8 (a performance which just about manages to stop me tuning out of all that awful singing - the fantastic SQ helps here too). Eliahu Inbal with the completed 10th is superb, and Fabio Luisi in Das Lied von der Erde well worthwhile. But the others....
1 - Daniel Harding....pretty straight and boring to be honest
4 - Ivan Fischer - very nice and smiling performance...but somehow doesn't get much depth out of it.
5 - Daniele Gatti.... still leaving me thinking he's not the man for the job at the Concertgebouw
6 - Lorin Maazel..... turgid, no other word for it.
7 - Pierre Boulez.... poker straight, worth hearing but probably not going to be anyone's favourite
9 - Bernard Haitink - I have to try this again.... Any Mahler 9 with Haitink should be an event.
Both sets are well worth having for the sound quality alone, and they can be found cheaper than the amazon links above.
Meanwhile, Riccardo Chailly and Leipzing Gewandhaus have also been releasing a cycle on Blu-ray, I have their 9th but not found time to listen yet.... need to be careful not to overdose, Mahler's 9th is a once-a-year listen IMO.