Both take 35mm film, both have 35mm lenses. Both take SR44 batteries, both have a meter, both are  manually wound, both are black, both are ....

Ok, there are a few differences. f/2 vs f/3.5 lens. Manual aperture & shutter speed vs automatic aperture & shutter speed. Manual focus vs zone focus. One is made out of brass and basically indestructible the other is basically cheap metal and plastic. Oh yeah, and the Olympus costs about 1 % of what the Leica will cost you.

Can you tell the difference?