I hold with those saying that any testing of these lenses is meaningless in regard to the OP's question. Our cameras are hardly made to function as testing devices and whatever subtle difference there could be it will be lost in the sea of inevitable mechanical imprecision of the individual elements that influence the resulting picture.
I think the OP is a victim of the frequent amateur boasting about lenses performance that has nothing to do with their real qualities. Best is to concentrate on the picture content you intend to catch and forget about technicalities you have no way to compare. Just my two cents.
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