How many Photographers does it take to screw in a light-bulb? Twelve --one to do the job while the other eleven stand around telling themselves they could do it better...
The Sigma has far less CA in the tree-comparison Duck posted, and looks sharper, as well. I see no real difference in the Bokeh in this example...the Sigma is superior in this shot
You need a course in reading comprehension tirmite, and the world of IP is far from a simple mine/yours scenario, but that would take patience and depth to understand.