In my experience with my P, Fed-2, Canonet G-III QL17 and Bessa T.
The Fed-2 had a more contrasty circle than the P so its somewhat easier to line up weaker patterns, course the viewfinder in general is not all that great.
The Canonnet GIII QL17 was a bit under the P in my opinion somewhat like my Olympus RC35, you can see somewhat but contrast isn't quite as good but close. (kind of a RF patch visible, but VF overall not as good to make it worth the comparison).
The Bessa T, well I haven't found anything yet (that I could own) that could be the T's rangefinder clarity and contrast (course its a baranack style so no viewfinder lines and such).
The main two things I don't like about the P's viewfinder, the viewfinder is easily subseptable to glare if you get hit with side light, and the RF patch while you can see it is not as contrasty as say a Leica M6 or M3. Mainly would just be difficult trying to focus off an area without as much contrast in the pattern in indoor or lower light.
Course despite that the P has been my favorite rangefinder all around, if I started from scratch, and I wanted to get an RF and I already had something aside for a decent lens I'd get a P over a Canonnet. But if you're seriously on a budget (ie: can't spend 200-300 for a body, or likely 100 to 300 for a lens) then the Canonet QL17 GIII is not a bad camera for something you can get around 50$ to 125$ now days.
I'm not too familiar with the Zorkis, I just heard the Zorki 4K is likely the closest to the P in terms of functionality, and that the Zorki 6 has the best viewfinder of the Zorkis. I'm even less familiar with the Kiev.