It's not that David or I feel that the BPO is a bad orchestra. Rather, it's that we both feel that the strengths of the BPO don't always work so well for Mahler's music. For me, the BPO often times sounds like an oversized chamber orchestra, rather than a full-blown symphony orchestra. Perhaps the Philharmonie somewhat helps in creating that impression. Obviously, they have excellent strings.
They have nice heft to the low strings, but the low brass don't always match. The trombones don't always cut through when they should, and the tuba has always been undersized for music like Mahler and Prokofiev, where the tuba is treated as an independent super-bass to the entire orchestra. Woodwinds are generally excellent in the BPO (great bassoons), but the oboes too often dominate the aural landscape. In regards to Mahler, the clarinets are sometimes too restrained with Mahler's characteristically high writing for them. There are plenty of times when Mahler wants his clarinets to just cut right through. By and large, their percussion department is pretty good. Yet, I've heard more miscounting mistakes from the kitchen dept. of the BPO, than I've heard from the VPO even (not always the best percussion by any means). One gripe I have is with the BPO is with the horns.
It's not that the horns of the BPO don't play well - obviously, they do - but it's that they're still using those rather small sounding Alexander horns. The Czech Phil., which had used the Alex. double horns for decades, has recently switched over to the expensive but versatile Schimd triple horns (and the VPO are still making the most of their indigenous single F horns). The best sub-section within the BPO's brass section, are the trumpets. I like the trumpets of the BPO far more than those in Vienna.
More than anything - and again, the hall may contribute to this - is that the BPO play with a dark, chocolate-like sound that works well in most Austro-German literature, but is not always to Mahler's benefit. High woodwinds should cut more, as should the low brass. These impressions were very much reinforced in my mind when I saw Barenboim conduct Bruckner 9 with the BPO in 1978.
Obviously, the strings and trumpets were excellent (as were the kettle drums). But the horns sounded much smaller than what I was used to in the states (at that time, most American horn players were using the Conn 8D), and I could hardly hear the tuba at all, even though he had been switching back and forth between two different tubas (what for?). The overall impression was that of hearing Bruckner played by a really great, oversized chamber orchestra.
Just within Berlin itself, both David and I have observed that the other orchestras in town - the DSO Berlin and the Staatskapelle Berlin - while perhaps not nearly so refined sounding as the BPO, often times sound more idiomatic for Mahler's music. This isn't to say that there aren't some obvious exceptions to these general impressions.
Both David and I feel that Karajan's live M9 is hard to beat, as is his 1975 recording of Mahler 5 (I don't feel nearly so strong about Karajan's M4 or M6, just from an interpretive basis). Some of the Haitink/BPO Mahler recordings aren't bad either. I don't care for the Haitink/BPO M6 so much in the first two movements (rather bland), but the last two movements are excellent. Certainly, Rattle's M10 recording with the BPO is pretty much spot-on, even though EMI's mediocre sound quality almost makes a muddle of it. These are solid exceptions to any rule, shall we say.
When it comes to the standard Austro/German rep., obviously the BPO are right at home. Personally, I think that the music of Richard Strauss suits them best. But even for the standard fare (Mozart/Beethoven/Schubert/Brahms/Bruckner, etc.), the Staatskapelle Dresden gives them a real run of their expensive money. In fact, I often times prefer the clearer textures and more burnished brass of the Dresdeners (and again, the halls may be a major factor here).
An interesting comparison can be made with Mahler 6: Abbado/BPO vs. Eschenbach/Philly. While I prefer Abbado's quicker, no-nonse tempi in the inner two movements, I like the sound of Philly in Mahler's music: strong low strings (just like the BPO); great violins (just like the BPO); hefty low brass; big, meaty horns; piercing trumpets (but not screechy sounding); clarinets that aren't afraid to shriek; excellent percussion throughout, etc. Granted, part of that difference is just the better sound quality from Ondine (not to mention Philly's new Verizon Hall). While there's certainly nothing wrong with Berlin's playing of Mahler 6 - for Abbado - from any techincal standpoint (Dave called it "Mahler lite"), I just think that Philly's sound-world is even better suited for the work. Don't get me wrong, I DO like the Abbado/BPO M6, especially when played back in S/A order (which works really well in this particular case).
Anyway, I've got to run. What works great for a Schubert symphony, doesn't always translate for a Mahler one. That's my point.