Jupiter 9 m42 or m39 on Nex

[bene]

The M42 is cheaper but is it or on par with the ltm version?
I'm asking because I have leica body but i doubt i will use it with on it so might as well get the M42 and save a bit.

 

[former member]

The earlier KMZ lenses are the best, and those are in Leica and Kiev/Contax mount.

Mu 1958 lens was much sharper than my 1975 lens. The latter is Contax mount.

 

[bene]

I plan to get from fedka are they reliable?
Basically I'm looking for a sonnar 85 mm that doesn't break the bank and probably m42 as i can't imagine using anything longer than 50 on an M=P
@ brian Thanks!