I have received my degree from the Normhead School of Skeptical Thinking...and to be honest, I put little or no confidence in any tests I see on the internet. There must be a thousand variables on most any test like the one done here......if you do all thousand of them, I won't have time to analyze the results......
The best test is to just buy it and try it...if you like it, that's great. If not, send it back and try something else.
I always find it sort of unusual that these tests always seem to confirm the greatness of what the testing poster owns or shoots with.......did anyone ask a Canon or Sigma guy to perform the same test?
Now that might be an interesting test!
Regards!