There are other issues you haven't mentioned. The Zeiss has a funky shutter speed display in the viewfinder - it's on the right side and hard to see if you wear glasses. Both the ZI and the Bessa have brighter viewfinders than the Leica, unless you're looking at an MP or a newer M7. Still, the M6 is a wonderful camera and being manual, like the 3M Bessa, will work without a battery. The Leicas are also reparable by reputable independent shops - DAG, etc. I'm not sure that's the case with either the Bessa or the ZI. BTW, I have used all three; I like the viewfinders on the R2 Bessa and ZI better, and only the Leicas have had to be repaired - mostly due to being dropped. I shoot the M6s much more often. Go figure.