DXO gives this lens the same sharpness score (18) as the Canon 24-70 2.8 II and the Tamron 24-70 2.8 VC. Perhaps I don't understand what their sharpness scores mean, but I'm pretty sure I've not seen any other review claim or show that the Tamron, however much they may like it, is as sharp as the Canon, or that the new Sigma, while a bit sharper than the 24-105, is also as sharp as the Canon 24-70 2.8 II. What am I missing?