I don't get it. Bryan's test at TDP is a complete blowout; not even close. The Sigma is sharper in center and much much much sharper than the 1.2L away from center and in corners, and the CA on the 50L is bad, while nearly non-existent on the Sigma.
In comparing any two other lenses, where there is no brand loyalty or investment-justification involved, that kind of test result would simply be a clear blowout, and there would be no further discussion. Not here though. Here we see the defensive comments and a retreat to the trenches of the intangibles like bokeh (which is not clearly different in any sample shot I have seen anyone point to specifically) and creaminess, and the supposed uselessness of test charts (but only for this lens).
There is a LOT of red-ring disease in this forum. Understandable I guess?