In my opinion, there's nothing odd about finding the Boulez M8 beautiful. It's very well recorded and very well sung (it was recorded in the Jesus Christus Kirche in Berlin and not the Philharmonie). The tenor, Johan Botha, is among the few who have truly done an outstanding job on the difficult tenor solos in Part II. The end to Part I is really wonderful - the best of anybody, IMHO. I just wish the end of Part II had more organ and was a bit more 'muscular' in the percussion. It seems that Boulez backs down, just when he should be going for the jugular. In the January 2008 edition of Gramophone, someone named Ken Smith did a huge round-up of Mahler 8 recordings. He considered a boat load of them and concluded that the Boulez was his ideal. I only own three 'complete Mahler' box-sets. One of those is the Boulez/DG. The other two are the 'Carnegie Hall' edition of Bernstein's original Columbia recordings, and the recent BR Klassik box of Mahler symphonies with the Bavarian Radio Symphony (I'll come back to that one). Interestingly, none of the other three conductors that you ask about were reviewed by Ken Smith (I'm not sure if either the Nott or Stenz were in print by late 2008).
I very much like the three that you mention. If somebody put a gun to my head and demanded that I choose just one recording of Mahler 8, it would be the Nezet-Seguin. His ending to Part II is greatly protracted, like it is on the Boulez. However, there's more organ on the N.-S., and a lot more muscle from the trombones (the gong is still a tad too distant). What's even better, is that N.-S. keeps the final Eb chord of the symphony dynamic, and not static sounding. He does so by placing a crescendo in the organ, followed by the entry and crescendo of the trumpets on top, followed by a crescendo in the bass drum. It works! There's just a great sense of a huge and important event with the Nezet-Seguin. The other two are also quite good.
The Nott is extremely well recorded and is probably a tad better sung than the Stenz (and by the way, not all of the soloists on the N.-S. are excellent, by any stretch). The end of Part II has plenty of organ - a nice sounding organ too! - and plenty of amplitude from the big gong. Before the N.-S., the Nott was my favorite overall recording.
The Stenz one has, for my money, the best overall ending to Part II of anybody. It's quite similar to the Gary Bertini one (same orchestra hall), but has just huge and nice sounding tam-tam smashes. There's not as much organ, but the big gong smashes make it thrilling. Overall, it's not as well recorded as the Nott. And similar to the Gary Bertini, the whole performance is relatively fast, except for the ending to Part II. Both Bertini and Stenz take the 'Three Penitent Women' passage quite swiftly, which is something I don't mind at all. That brings me back to that BR Klassik box set.
Perhaps my personal favorite M8 from a European source is the Colin Davis one with the BRSO. It was originally issued on RCA, but the sound is better in the BR Klassik box (there are some other really good performances in that box too). In a number of ways, its an idiosyncratic choice. Some of the vocal balances in Part II are skewed, particularly through the '3 Penitent Women' passage (which is taken rather slowly). However, the choral work is outstanding on this one, including the Tolzer Boys Chorus. Also, Colin Davis just sounds so relaxed and 'natural' with this work - somewhat rather similar to Horenstein in that regard. I chock it up to all the experience Colin Davis had, performing and recording all of those huge Berlioz works (which in some way, are a precursor). He also has an excellent tenor in the younger Ben Heppner, and the big tam-tam smashes at the end are huge (a tad faster than I like, but that's OK). It's a comfortable performance that keeps my attention from start to finish (excellent Part I), even if I sort of cringe here and there in the latter stages of Part II. I'm generally not a sycophant of conductors - I view them as a necessary evil - but Colin Davis is among the few whom I almost always seem to like.
There are, of course, other very good recordings of M8. From the 1980's, I don't think we should discount either the Gary Bertini or Elihu Inbal ones. For me, both of those were a significant step forward from the highly touted Solti of 1971 (which I've never warmed up to).
The other thing to be considered are DVD's. I now have four of them! Those are: Bernstein/V.P.O. from Wien's Konzerthaus (1977 or so); Chailly/Leipzig Gewandhaus (a superb, all around performance and recording); Dudamel and his full cast of a thousand (and it's quite good), and the Paavo Jarvi/Frankfurt R.S.O. one (which I got for the fine M7 that comes with it).
There are, of course, some very good 'pirates' that are floating around out there. I have a pirate of Michael Tilson-Thomas/S.F. Symphony doing M8 from 1991, that is vastly superior from the official recording that SFS Media released about ten years later. I'm not a fan of MTT's Mahler at all, although his earlier recordings were genuinely superior to his later offerings (his L.S.O. M7 is quite good).
Now, if they were to put this out on DVD, perhaps the Granddaddy of all Mahler 8 performances - for me - might be the relatively recent one that Franz Welser-Most/Vienna Philharmonic did from Vienna's Konzerthaus that was streamed on Takt1. It's no longer available at Takt1, which make me wonder if it might someday be made available by C-Major or some other dvd label. It just seems to have been too good to be allowed to just vanish into obscurity. It was excellent in every respect.
Hope some of this helpful.
