You asked
Leica apo macro elmarit sl 100mm f 2 8 vs sigma 70mm f 2 8 dg macro art?
Both are sharp autofocus macro lenses at f/2.8, but they suit different shooting.
The Leica APO-Macro-Elmarit-SL 100mm f/2.8 is the longer lens. It keeps you further from small subjects, which helps with skittish insects and flowers. It's made for L-Mount only, and it works on full frame and APS-C Leica bodies.
The Sigma 70mm f/2.8 DG Macro Art is the wider, more flexible choice. It's sold for Canon EF, Sony E and L-Mount, and it fits a much longer list of bodies. It also feels more natural for general close-up work, since you're nearer the subject.
My pick: if you already shoot L-Mount and want reach for tiny subjects, go with the Leica. If you want one macro lens that works across systems, or you're on Canon or Sony, the Sigma is the sensible buy. Neither is stabilised, so a steady tripod or a fast shutter helps.
Written by Claude from this site's pages.