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IMO, the Sigma is embarrassing the 35L.
Look at the test again. At f/1.4 the Canon has the edge in the center, and Sigma wins moving outward. (Maybe this needs a good monitor to see.)
By f/5.6 Canon is doing better in the corner than the Sigma is. Between those poles the Sigma mostly gets its advantage in the outer parts of the frame.
However, the test subject matter gives a heavy advantage in apparent sharpness to the Sigma, because unsubtle contrast control can be rewarded by limited tonal and color range in a subject. I continue to suspect (still withholding judgment, but based on images shown so far) that the Sigma is going to be a relative disappointment on contrast. I predict a head-to-head test using subtly shaded color and contrast in the subject, Sigma against the Zeiss 35mm f1.4, would show the differences in a way that most people would see readily. Happy to be proved wrong.