I've been shooting these two side by side for the past couple of days: Left: Sony A7R with Leica Summilux M 35mm f/1.4 ASPH (FLE); right: Olympus E-M1 with Voigtlander 17.5mm f/0.95 Nokton Both combos are pretty sweet to use. I think I could use either and have little need for anything other than the occasional short telephoto. Some key differences: 1) The Sony/Leica combo is smaller. This will surprise some given that the Sony sensor is 4x larger than the Olympus, but lens size isn't necessarily tied to format/focal length/aperture. For example, a Zeiss 35/2 for Nikon SLR is much larger than a Nikon 35/2 for the same system, and a Zeiss Otus is much larger than any Canon 50mm lens. All depends on what the lens maker is trying to accomplish (see point 4 below). 2) The Sony/Leica combo has incredible resolution. The sensor is much higher resolution, and the lens is much sharper. The differences in comparative detail when pixel peeping are stark. Will post some examples of that later in this thread. 3) The Olympus/Voigtlander combo has smoother bokeh. Not necessarily better but definitely smoother. 4) The Olympus/Voigtlander combo has a far shorter minimum focus distance. For example, this is as close I as can get to the Christmas tree with the Sony/Leica (entire frame, resized): whereas this is how close I can get to the same tree with the Olympus/Voigtlander (entire frame, resized): 5) The Sony/Zeiss will run you just over $7700 (including Novoflex adapter), the Olympus/Voigtlander just over $2500 (current B&H Photo pricing). 6) Handheld, low light, high ISO results are pretty much a wash. The Voigtlander is a stop faster, but the magnificent Sony sensor more than makes up for that. Meanwhile, the class leading in body image stabilization (IBIS) of the Olympus just about evens the score as far as I am concerned, keeping in mind that image stabilization won't freeze a moving subject and high ISO won't help you show subject movement. 7) The Olympus viewfinder is a touch better than the Sony, but more importantly, the view through the Olympus viewfinder is steady (due to IBIS) while the Sony viewfinder is shaky when magnified for focus verification. Meanwhile the magnified view through the Sony is sharper when using both lenses wide open because the Leica lens is sharper wide open than the Voigtlander lens is wide open.