Forgot to mention I shoot with a 6D.
I've shot with the Sigma and wasn't that impressed, but then again I was comparing it to the Canon. I don't want to pay that high of a price if similar image quality can be had with the Canon 1.8 at half the cost.
If anything, compare it to the 1.2 and not the 1.8. I have used all of them, and like you I would love to have the 1.2, but cannot afford it now, which is why it was obvious to me that the Sigma was the next best.