IMO.
In 2017 I had LNIB Planar 50/2 ZM with original hood and filter. It is best neutral 50mm lens I ever used for B/W. And silver Planar is nice on M3.
By same time I owned Nokton-M 50 1.5 ASPH and I find it superior to Planar for B/W. A lot more character (Planar gave none in my hands) and no focus shifts just as Planar. Film and digital BW, Nokton-M 50 1.5 ASPH is lovely lens. Dare I say, classic.
But...
Both were weird on handling for me, never impressed me on colors with M-E and I sold both to get Cron 50 IV. This lens is not sharp comparing to Zeiss and Viogt on M-E, it has focus shifts. It is just as Planar on BW, so-so. To be honest, I'm not impressed with this lens on BW film at all... Sharp and this is it.
But it is incredible on color. Especially on digital M. It renders colors naturally, but punchy enough. Bokeh and OOF transitions also makes this lens outstanding. And it has much more acceptable handling for aperture and must have to me focus tab without too long focus throw. Currently it is 1K$ lens on the market...
Where are some less expensive Leitz and Leica made lenses to consider for M3.
Speaking from my own use, M3 included for some of them, or on M4-2:
Collapsible Cron in M mount. Probably best BW film lens I ever owned. Sharp and CHARACTER. But I never tried it with color film.
Rigid Cron was even more sharp on BW, yet less... lees pleasing. Very close to Cron IV I have for now. But it was amazing lens on color film. Very sharp and not flat at all.
Elmar 50 2.8 v1 and 50 2.8 v2. I had V2 which is also called Elmar-M. Tessar rendering on BW film. Punchy and contrasty. Outstanding on darkroom prints, just as collapsible Cron, just more modern in character. But.. it was too tessarish on portraits for me. And I didn't liked handling. Collapsible Cron is more compact then in use and has better build, IMO.
I also had original Summarit 50 1.5 on M3. Probably most toughest build lens I ever have and most softest (for scratches) glass I ever touched to deal with one fungus spot.
Results were usable at 1.5 if object is in the middle. From f2 it was fine Leitz lens on BW and color film. Enough sharpness and contrast and it was visible what it is Leitz lens. Not Jupiter-3, which I keep as alternative for any Leitz, Leica 50 1.5/1.4 ever build. For BW film, of course.
I gave up on Summarit 50 1.5 on M3 because it was too heavy.
IMO.