Zorki : the zorki 4 VF is very bright, with diopter adjustement, and huuuge, so huge that it rather covers a 35mm frame. Focusing is fast and easy. But you need to be careful not breaking the shutter by changing the speeds before, but you get used to it very quickly. Also, the shutter is quite noisy, thou not as much as for a SLR.
And you can get nice, cheap lenses from 28 (hm... did somedy say "orion"??) to 135. Above is no use having a rf camera.
The Kiev : it is a completely different philosophy.
as somebody said before, it has the longest rf base ever (along w/ the contax II-III of course). The holding is not really a problem, even more you're much steadier.
The shutter is very quiet, incredibly solid and hard to repair (never tried on mine)
You need to select the expsure first, but it does not break the shutter if you don't.
Focusing is a bit slower, and the vf is very dim if you've tried a Zorki before. If not it seems to be all right 😀
And contrarely to what was said before, small adjustement of the RF is very easy, just need a pair of screwdriver, a tripod and scotchtape for that. See the Kiev Survival site.
In a nutshell : Zorkis are smaller and more user friendly, they are basically Leica copies (in spite of their appearance from the Z4), but Kiev are really quiet and funny to use. It's an ideal camera for a concert use. And above all, you can use it as a defensive weapon whithout to much harm. For the camera, not for the poor guy you'd have hit with it!!