Zorki generally are built better, to a greater extent more Leica-like, than FED. When a FED and a Zorki of the same age are compared, the Zorki would likely edge out in terms of handling feel, build, and finish. But function-wise, a FED is no less better as a shooter. Wolves's observation is the same as mine.
"FEDKA" was never really used popularly to call FED-1. it was proposed, but the cameras were known as FED. Even "FED-1" is unofficial. The cameras were only known as FED when they came out. It's only now that they are called as such for better identification. So the model progression is more like FED, FED-2, FED-3....
The "expensive" FED you are seeing are the prewar ones. If you've understood what you read, you should know that these aren't the best to get if you plan to shoot with them. The NKVD FED for instance don't have standard lens registers so lens-changing is not possible. The focus pitch of the early FED50 which came with them is also not standard and varied from sample to sample.
Are you planning to get one or both? For what purpose?
FED or Zorki (1) are not for new RF shooters. The small squinty VF and separate RF may upset you. If you did not like what you saw through the FED-3, you probably won't like what you'll see through FED or Zorki eyepieces too.
And the bottom-loading procedure may not be for you.
