PeteH said:
Stop me if this sounds a bit weird

- but in a funny kind of a way I think the restricted sound quality of the Busch versions almost adds to them, sort of. It's scratchy and oppressively close, to be sure, but I wonder if an immaculate modern recording would actually have diminished the amazing sense of intimacy - privacy, even - that makes listening to those recordings feel like some kind of intrusion.
There was a fellow, from Diapason, André Tubeuf, who would agree with you. He was an old recording maniac, and was the reviewer of most Beethoven works (including the Bush records you mentioned). He used to say that recordings of the old days actually sounded better than the modern ones. 'What is so important about old recordings?
Le son (the sound)'. I remember quite clearly I was completely fed up with both that kind of talk and his reviews - for instance: 'in Arrau's Beethoven one could argue that the forest may be obscured by the tree; but with Arrau the leaf itself is a world' – well, someone that talks like that is playing with words and not speaking about music.
What I mean is, I think he was the ultimate snob, a kind of snob one can only find in the Paris 'salons' where all the silly people want to hold 'original' opinions (only shared by the whole group, of course). (by the way, it is THE place to use 'Bluffing your way through Philosophy': I actually did it and the result was marvellous!).
Now
I am most definitely not calling you a snob. What I am trying to say is that one can like the very focused and closely miked old recordings because sound is, in fact, somewhat more present, more intense. For instance, Casal's Bach cello suites have that very quality; and some of the older recordings by Walcha too (the awesome Partita Sei gegrüsset). There is also another thing. Some players of the mono era were, indeed, more intense, more relentless, more 'into music' (this is by no means general, but I believe it is true about the Busch).
But Tantris is right: listen to live music. If the musicians want rough sound they can make it (with strings almost everything is possible). So perhaps you like the Busch because there is a concentrated nature about their playing which is conveyed by bad recording technique and a raw sound and probably not by the musicians themselves.
I have been subject to the very same phenomenon with very old recordings of organ music. When I managed to listen to the same instrument live, I would be amazed, because it sounded so different (on the same stops).
That is why the sound engineer is so important: he may actually change what the musicians wanted to convey.
Anyway, this is an interesting subject: how performances can be enhanced or destroyed by the engineers.