Well, in the spirit of being more specific, I'll tell you one box set, or set of box sets, I'll be staying away from: the BIS complete Sibelius edition.
I know I mentioned it before after a preliminary look, but this time - armed with a better mental knowledge of Sibelius' list of works thanks to
www.sibelius.fi - I had a thorough look at the contents. It takes comprehensiveness to truly ridiculous extremes. I could cope with something like piano and orchestral versions of songs, or recording first versions when the revision happened years later, but here we have every sketch, preliminary thought and piece of homework they could lay their hands on. It's full of world premiere recordings, but often because the recording is of something so mind-numbingly trivial only the most dedicated scholar would ever want to hear it.
I can cope with a piano transcription of the
Valse triste, but does anyone really need both the 'preliminary transcription' and the 'definitive transcription'? Isn't the whole damn point of the 'preliminary transcription' that he was still working on it?!?! I'm quite sure there's stuff in here that Sibelius would never have intended anyone hear, and if he'd known someone was going to do this he would have built a bigger bonfire when he was burning works later in life.
There are 13 multi-disc volumes in the edition, and I'd say that almost all of them drown the interesting material in a sea of distractions.