I am mainly interested in comparing their viewfinders, and ergonomics in general .
Going by this thread title of Zorki 4K vs Leica M (not Barnack):
The viewfinder in a Leica M is very bright, no colour cast, has defined frame lines that automatically correct for parallax, and has a defined bright rangefinder patch.
The viewfinder in a Zorki is much more dim, smaller, has no frame lines, no parallax correction, and has a dim ill defined rangefinder blob/patch.
There is no comparison.
Not as long as they are selling at inflated prices.
They're not inflated. That is what people are paying for them.
I have a Zorki 4K, Fed 2, Kiev. And Leicas.
The Soviet cameras are cheaper. If you are looking for someone to say 'hey George, there's no difference! Just get a Zorki!', well, no.
Before I load a roll of film in any of my FSU cams, I need to exercise the shutters. Fire them numerous times at all speeds, otherwise the speeds can be erratic. And my cameras were bought from very reputable sources, had been serviced and are in great condition. Just the act of doing this is tiring, as the film speed dials are not great to use. Sharp edges, need to be lifted and rotated fighting the spring mechanism friction. Fiddly to lower accurately into the desired speed setting.
Load a roll of film. The first few shots can be fun, as you are taking pics. But if you plan on shooting several rolls of film a day, you'll notice that it gets less and less fun and smooth as the day goes on. These cameras don't work with you as good gear does. They kinda wrestle with you as you take pics, which tends to grate.
Pick up a Leica, and they are just heavenly to use. Full stop. Period. End of sentence. A Leica M works with the photographer, I never get tired of shooting with one, no matter how much film I shoot in a day. They make you just want to keep on shooting. The Soviet cams make me want to put them away after maybe a dozen exposures. And think about rewinding the film and loading it into a camera I actually enjoy using.
I will say that my Soviet lenses are really really good. It's almost the saving grace, almost because you can buy any cheap Japanese camera that also has really really good lenses. A Pentax SMC 50mm f2 for $25 is just as good if not better than any of my Jupiters, Helios etc lenses. So using Soviet cams for the glass as the excuse doesn't hold water.
Really the next best thing to a Leica M is a Nikon S series RF camera. I bought my gorgeous S2 with 50mm 1.4 lens for under $400.
Anyway, here are my fantastic FSU cams - all for sale! Out of these, I like the Fed2 the most. It just feels better in hand,.