I own both an AKG C34 and a Nevaton MC404.
AKG C34: My mic is the variable pattern version. Most of the time I use it in MS, sometimes Blumlein. This is a fine mic, but it’s a bit bright. It is not my first choice to record Chamber music, especially strings. Violins recorded with this mic often sound too harsh. The HF emphasis is above about 8 kHz and a little eq can make strings sound much better. The mic is a little noisy too, but in practice I have not had a problem with noise. Perhaps that’s because I often use the C34 to record jazz combos, and in that application the mic is just about perfect.
The C34 is small for a stereo mic which is a plus. I don’t like having to use the remote box to select patterns; I’d like the pattern selection switches to be on the mic.
In the USA, a C34 sells for about $2000, or perhaps a bit more. That is, when you can find one for sale. Seems like I see one for sale in the USA about once a year, but I’m not a microphone dealer by any means. In Austria they are less expensive and more easily found for sale?
BTW, the C426b is a superb microphone: very smooth and quiet. I would not hesitate to use a C426b to record Chamber music or strings. It is a LDC, but that is not too much of a problem with small ensembles since no instrument is too far off axis. I cannot remember making a bad recording with my C426b. The mic is kinda big, and the shock mount is finicky, but the sound makes up for it all. In the US, the C426b sells for around $2300 (when you can find them) which is not much more than a C34 and worth every extra penny.
Nevaton MC404: This might not be much help to you because I believe the MC404 uses a different capsule than is used in the MC47 & MC48. I believe the MC404 has a 28 mm capsule and the M47 has a 25 mm capsule. So for what it’s worth, the MC404 is a fine microphone: quiet with a neutral balance. I use the MC404 as the Mid mic in a DMS setup to record a bell choir and the director told me it was the finest recording she had ever heard of a bell choir.