I do a lot of city shots at night, I can tell you that the 17-40 has the best flare control of any lens I've ever used. Both for controlling artifacts and veiling flare. If your looking for resolution mostly, I'd look at the Tokina 16-28. I tried the 16-35 II and found it wasn't as good in contra light as the 17-40 and not as sharp as the Tokina, but it was second best at both.
I'd look at the Tokina 16-28.
Mine just came in yesterday, virtually worthless at f/2.8 for anything sharp. Also, focus motor is quite loud. I can live with that but when focussing from wide to narrow or visa versa, there is almost a grinding sound! Doesn't sound good at all, I can only picture little pieces of plastic or metal being ground down inside the lens body! The terrible sharpness at f/2.8 and the grinding noise will win this Tokina a place in the return mail! I will let them send me a new copy as I noticed the barrel distortion was really slight, even wide open at 16mm. That part was pretty impressive.
If the new copy fixes the sharpness issue at f/2.8 and the grinding sound coming from the AF, I'll keep it. If not, I'll be sending it back and moving toward the Canon ef 16-35 f/2.8 II.
Also, the Tokina lens is very heavy. I have a lot of heavy lenses but this one seems very heavy for it's relatively small size... I'll have it mostly on a tripod so that won't matter to much to me...
The vignetting was fairly normal to heavy at f/2.8 but it was extremely minimal at f/4.0 and above. Very pleased with that. CA was the same, very well under control... Hopefully, given the sharpness issue and the grinding, I just got an ill copy...
I can add the filter system to it and still be well under the cost of the EF 16-35mm II