In my HMO their is more than just the extra stop difference between the 17-40 and the 16-35 II. I have had both, compared them side by side and the 16-35 has higher resolution, less chromatic fringing, and less vignetting. You get what you pay for.
But is the $800-$1000 difference really worth it? Would your client or friend know the difference? For most and I am one of them too, we are our own biggest critics and it is usually the photog themselves that will be able to tell the difference and from the pictures that I have seen from both lenses, it is quite difficult to tell. Both are stellar lenses and with the money I will save if I go with 17-40L which I will be, I can buy another backup body or maybe another lens.

. Now, need the snow gone soon
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