I'm looking to grab a reasonably inexpensive MF camera (<$500), but I'd like to use it primarily hand-held for street photography, with the occasional tripod shot - macro, product, landscapes, etc. I don't necessarily need it to have a built-in meter, and it certainly doesn't need to be AF, but I would prefer it to have an MLU option. I'm also looking for a system, so availability of lenses/backs/accessories should rank pretty high. For reliable hand-held use I'm looking for either leaf shutters, or well-behaved mirror SLRs. For street photography I might prefer a WLF, but I'm OK with a regular VF.
After a few months of research, here's what I think my options are, but I'd like to hear some personal opinions on these:
1. Mamiya 645: I played around with one in my local camera store the other day, and the shutter was surprisingly quiet and soft. I think it was one of the earlier models of the M645. I can put a WLF on it instead of the prism, and it comes with MLU, but doesn't have interchangeable backs. Good lenses, and widely available accessories.
2. Pentax 645: Most SLR-like, with a wide range of lenses and accessories. Only comes with prism, no MLU unless I get the NII (which is out of my price range), no WLF. Not sure how quiet the operation is, nor how dampened the mirror mechanism is.
3. Kowa 6MM/66: This was a bit of a surprise when I ran across it because it's not as mainstream as the others. They're reputed to be very quiet and with low vibration because of the leaf shutters, which also give them high flash sync. Limited access to lenses/accessories, but overall pretty cheap as a system. Some mechanical issues here and there, but nothing that can't be worked around. The 66 has changeable backs, but loses MLU. It's also 6x6, which could come in handy and I can always crop to 6x4.5.
4. Bronica ETRSi: This one gets rave reviews, comes with WLF, metering, backs, leaf shutters, MLU, and lots of accessories and lenses. I haven't held one to know how quiet or soft the shutter is compared to the Mamiya 645 I tried, but it holds promise.
5. Others: I looked at Bronica SQ-Ai, Bronica EC-TL, but when I played with them in the store the kick from the mirror was quite severe, so while they began as the camera systems with the most promise, they fell off the grid because of that. I looked at the Rolleiflex and it was very quiet and free of vibration, but I think I want a bit more flexibility than a TLR offers, and besides it was out of my price range, as were the 'blads and the Contaxes.
Anyway, I'd appreciate any thoughts or considerations I haven't thought about in settling on a camera system to get into this format (aside from my Holga).