One other point probably more important than lens quality and that is manual focus. The AF can get very confused in low light (especially the sMKIII), the lenses on the Canon / Nikon have no stop for infinity. I have tried manual focus with them, but for some reason I can't get infinity everytime, it looks right in the camera but is often off when viewed on screen. A problem most of my colleagues encounter also, it's been discussed over and over amongst some of us. With the Leica lenses I would tape them to infinity.
Kevin.
For what it is worth my Zeiss ZF 100mm f2.0 is tack shart at infinity when reaching its infinity stop.
Cheers,
Bernard
