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To answer the questions, to me AF for a 1:1 macro lens is nearly irrelevant. I do (as most other macro photographers) macro focus fully in MF. The Canon lens itself is a lot better when AF capabilities are compared between those models, here the review is accurate. This review here also does not mention the much smaller aperture the Sigma lens can have. Anyway, my point is that all lens reviews of this site always end in favor for Canon.
Actually he does mention the smaller aperture the Sigma lens can have. The Sigma goes to f/45; the Canon goes to f/32. He writes, "Since DOF (Depth of Field) is very shallow at close distances, you will likely find yourself using this lens stopped down significantly. But maybe not to this lens' uniquely narrow minimum aperture of f/45 (f/32 with Nikon and Pentax mounts). Unfortunately, diffraction causes images to go soft beyond f/16 or f/22, so this extreme-minimum aperture is not helpful to me."
The Canon lenses are often more expensive and have the advantage of being built by the maker of the camera bodies instead of a third party. It's not surprising to me that they are often better, perhaps not in every detail, but in important areas like autofocus.