If you are having trouble comparing the lenses, the key issue is bokeh. bokeh bokeh bokeh bokeh. you don't spend that much money on a lens if it didn't render out of focus highlights smoothly. The sample comparison 1/5th away from the beginning shows this and is the sole reason of owning this lens. Look at the girl in the image and then stare at the top left corner of the comparison. The canon wins: no contest.
I've owned the sigma and realized that was what photographers were after and sold the lens.
Mine had no focusing issues and performed well, just not as smooth as the 85L