I already have a Sigma 35 and it is indeed an amazing lens.
But I tend to prefer the 50mm focal length. The Canon 50/1.4 has been okay, but it's rather uninspiring compared to the Sigma 35. Perhaps I'll just stick with the Canon until Sigma releases a new 50/1.4 in the art line. I noticed that they released a 30/1.4 Art lens for APS-C today, as well as 3 mirrorless Art lenses. Wish they would have done the 50/1.4 instead!