These cameras are fun. Don't expect them to be professional-quality tools - they aren't. However, they're a blast to use if you're in the mood.
I frankly prefer the Zorki 4 to the 4K. I know that the knob wind is harder to use and slower, but it feels like it belongs on the camera whereas the wind lever doesn't.
The older Zorki 4s are nicer than the newer ones. They have engraved shutter speeds instead of silkscreened (the "Zorki" logi is engraved too) and the camera has appealing vulcanite instead of nylon. Both models work fine, but the earlier models are more pleasing somehow.
Unfortunately, my 4 is a newer one but it works very well at all shutter speeds. (I have a 4K too but I seldom use it.) My Fed 2b and 3a cameras are nicer in some ways because of the engraving and the vulcanite, although the 2b doesn't have the full range of shutter speeds.
Collect the whole set. I have about six of these beasts. They're all fun.