<p>Have you made your decision? Several years ago I asked this same question of a well known photographer and he recommended the Zeiss as a companion to my Summicron. I have been very happy with the Zeiss and often use. Truth be told I have kept a record over the last 4/5 years of which 50mm I have used with my Leica. (I also have a 50mm Elmar-m.) What stands out is the image captured and not the lens. Personally, the only lenses that I have found to be distinctly different are the old screw mount lenses, the Summitar and the Elmar f3.5. As a caveat Good photographs will compensate for the lens.</p>