You asked
Olympus m zuiko 12mm f 2 vs panasonic leica dg 12mm f 1 4?
These two are the same 24mm-equivalent wide prime on Micro Four Thirds, and they differ mainly in speed. Both fit the same long list of OM System, Olympus and Panasonic bodies, and neither is stabilised.
The Panasonic Leica DG 12mm f/1.4 is the one I'd pick for low light and for a bit more background separation, since f/1.4 gives roughly the depth of field of f/2.8 on this sensor. The Olympus M.Zuiko 12mm f/2 is a small, metal lens, and at f/2 it gives about the depth of field of f/4. If you mostly shoot in daylight and want a compact everyday wide, it's a sensible choice.
If you're new to the system, start with Micro Four Thirds to see what else fits your body.
Written by Claude from this site's pages.