Following recommendations I've found in Tony Duggan's site:

   http://www.musicweb.force9.co.uk/music/Mahler/

I've bought recently from my favourite mail order record shop the
recordings below:

MAHLER - Symphony no. 1 - London Symphony Orchestra/Jascha
Horenstein/Unicorn-Kanchala.
A marvellous interpretation, there is no doubt about it.  I could hear
things that I couldn't in my three previous recordings:  (1) Rafael
Kubelik's (DG 'The Originals'), (2) Bernstein's (DG, live, with the
Concertgebouw) and (3) Abbado's (DG, live, with the BPO).  It's very
impressive the way Horenstein builds the tension in the 4th movement to
reach a real wonderful finale.  The choice of tempos in this movement
is, IMHO, odd.  Just to compare:  Kubelik is the faster one, with 17:38,
followed by Bernstein (20:09) and Abbado (20:35).  But Horenstein takes
22:14!  The only drawback of this recording is that I had to put the volume
button in a high position to really appreciate the music (otherwise it's
almost impossible to listen to the trumpets "in surdina" in the first
movement).  Is it my problem or is it due to my poor equipment? Besides
this, the record company should put the Lieder eines fahrenden Gesellen,
like in Kubelik's DG, to fill the rest of the disc.  By the way, I liked
the sound in Kubelik's recording, despite the 'artificial' brass.  Summary:
if two's company and three's a crowd, I'm satisfied with four.  Wonderful,
my search for a definitive Mahler 1st has ended.

MAHLER - Symphony no. 5 - New Philharmonia Orchestra/Sir John
Barbirolli/EMI 'Great Recordings of the Century'.
I think that this recording deserves its classic status.  It's not
necessary to say more.

MAHLER - Das Lied von der Erde - John Mitchinson, Dame Janet Baker/BBC NS
Orchestra/Raymond Leppard. BBCM 5012-2.
I'm a little bit disappointed with this recording.  The sound is not so
good for its age (1977), and I didn't like John Mitchinson's singing.  In
my opinion, Julius Patzak (DECCA Legends, with Ferrier and Bruno Walter) is
the reference to which all other tenors should be compared with.  And in
comparison with Patzak, Mitchinson pales.  The real gem of this recording,
as Tony points out, is Dame Janet Baker - absolutely wonderful singing,
what makes this recording worth acquiring, besides the price (4.99!).
Summary:  interesting, especially for the singing of Dame Janet Baker and
the conducting of Raymond Leppard, but my search for the best Das Lied
still goes on.

Wilson Pereira.
Natal, Brazil.