I finally got my hands on a Sigma and tried it today. I liked the sharpness , although that wouldn't alone be at all a reason to sell mye 35 L. I like the built quality, but not the weight and size
Compared. I really liked the color and contrast and the bokeh seemed similar. The
BIGGEST QUESTION for my wanting to test it was in terms of AF speed, all info I have found point to the direction that they are very much a like, but that's
Completely false, it's WAY slower, very dissapointing. I haven't done any research if the 35 L is faster on the 1dX and other people have tested on a 5d not seeing the difference. But on the 1dx at least the AF of the Sigma is much slower and to me, that will always be what I look for in a lens.
Get the 35 L sharpness is a result of a properly focused image.