Ditto for the Solti set. You can hear every detail with ease. There are so many great Mahler recordings--every conductor and his brother have recorded a complete set at this point.
Not really. The analog recordings in that cycle (5, 6, 7, 8 & 9) suffer from a constricted spectrum and don't have the full dynamic range of the later recordings and are generally too bright. The 5th has a few moments where the sonic power of the CSO exceeds what the equipment can handle. The digital recordings in that cycle (1, 2, 3 & 4) are unfortunately typical, glassy early digital Decca recordings that again are too glassy and bright. That being said, Solti has of course one of the finest 2nds, 3rds, 6ths and 8ths on record. But if you want a consistently excellent Mahler cycle, I would get Kubelik or Chailly. I think those two are at present the best value for a complete set. If you want to mix and match, I would get the following, if I had to restrict myself to one recording of each symphony:
1: Kubelik/BRSO/DG - completely natural and fully at home in the odd folkloristic juxtapositions of this symphony. The BRSO's playing is superlative.
2. Haitink/RCO/Philips - still to me the finest recorded performance, though Solti and Kubelik are not far behind. Every detail shines through with Haitink and makes sense in the context of the whole.
3. Haitink/CSO/CSO Resound - this is not out yet, The CSO is issuing it next month! I heard the live performance where this was recorded and it was one for the ages. Some of the finest playing I have ever heard from the orchestra and Haitink knew exactly where he was going with the piece. Also, the performance had the kind of spontaneity often missing from Haitink's studio recordings. If the engineering is half as good as the performance was, this will be the recording to have.
4. Kletzki/Philharmonia/EMI - Kletzki somehow manages to find the fine balance between the bucolic and the parodistic in this symphony much better than anyone else. This performance of the 4th evolves so naturally it seems as if nobody ever needed to rehearse it at all.
5. Chailly/RCO/Decca - probably the best performance in spacious modern sound. The sonics of this recording must be heard to be believed. The Concertgebouw in its full glory. Solo horn Jakob Slagter and solo trumpet Peter Masseurs do superlative work here.
6. Solti/CSO/Decca - the raw energy and intensity of this performance is yet to be surpassed. Yet, Solti finds the time to smell the flowers in the slow movement and CSO principal horn Dale Clevenger delivers a solo of such refinement that you just want to melt away.
7. Barenboim/Staatskapelle Berlin/Warner - the 7th seems to be one of the toughest Mahler symphonies to bring off. It often devolves into seemingly unrelated melodic episodes or into an aloof, proto-modernist musical exercise. Barenboim here manages to bridge the gap and create a flowing, living, breathing performance. He is aided in no small part by the magnificent palette of colors of the Staatskapelle Berlin.
8. Chailly/RCO - all the tautness of Solti's performance, but with far better sound, more attention to detail and a warmer, richer palette of colors. Among recordings in modern sound in a class of its own. Again, the Concertgebouw unleashes its unparalelled Mahler heritage and experience.
9. Barenboim/Staatskapelle Berlin - what I said about his 7th you could repeat here. Just a fantastic performance with a rich, dark sound very much appropriate for the mood of this work.