The 85 art is already neck and neck with the 200 F2 as far as IQ goes. The 200 is barely.... barely... better. This 135 will match and/or exceed the 200 F2 performance.
I put this together showing the sigma MTF charts and what I do is compare them to the lens rental data to get a baseline of how they compare which led me to see the 85 Art was really sharp and this 135 will be even better.
What amazes me also is the fact the 14 out performs the 20 and the 24.
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forum: Photography Industry News
I have no doubt the 135 will topple other 135's, it's just that I'm not too concerned about mtf's when it comes to my people lenses 
Among my favorites are a double gauss 50, samyang 85, neither are MTF kings. I was hoping for something more manageable in weight, since I may do some serious travel where weight is a very real concern, and I've already have heavy high MTF lenses for my landscape shooting, my other stuff has to be lightweight.
I'll still consider the 135, which I use for a lot of formal shooting, where weight is less of a concern.

(24Lii, sigma 50A, 135L), and for the other ends of the spectrum, sigmaEX 14mm2.8 and sigmaEX 100-300F4.
