After a few years of running around with a CL, I'm convinced it's an awful body to use my V2 50mm Summilux on. That dense, heavy lens seriously unbalances the camera. I'm therefore thinking of buying a user-grade conventional M body so I can use that wonderful Summilux.
I have absolutely no desire to own a meterless body, though, so it's M6, M7, or MP, if I stick to Leica-made. Seriously looking at Zeiss Ikon, too, but...
I would be using it strictly with the 50mm focal length. I don't like the look of anything wider than 40, and I don't enjoy using telephotos on rangefinders. A camera optimised for 28mm or 35mm lenses would be wasted on me. I'm keeping my CLs to use my 40.
Degree of automation, type of meter readout, rewind, black vs silver...none of that matters to me. Price isn't much of a factor, either, as long as I stay in the user-grade used market. Rangefinder accuracy, though, does matter. If any of these three has an edge over the others as regards their rangefinders either being more stable, more precise, or just plain easier to focus, an f/1.4 lens wide-open would be my excuse for wanting to know. I do an awful lot of low-light stuff.
So, what's the knee-jerk answer for the ideal metered, 50mm Summilux rear cap for photographing black cats in coal cellars?