You are a professional doing this? If there is no + as I understand the financial issue is important to You, then without hesitation take the Sigma.
If it brings some income or You are photographing in the Studio, and native Kanarovska blaze, of course would be preferable. And faster and synchronize better build quality again.
I was choosing between the 430 II, 580 II. Took the 430, as the needs in page not as big. The Studio don't like the extra 30% of the weight I don't need, reload speed, 430 arranged.
So I think You first need to decide for what purpose you need blaze.