You are welcome
I had this same question and went with the 17-40 for two reasons.
1. there isn't a very pronounced depth of field with a super wide angle, so the difference between f/2.8 and f/4 is negligible.
2. you have the 5D3 as well, which is fantastic at stupidly high ISOs, so the loss of one stop isn't a very big deal
With those two factors in mind, at half the price of the 16-35, the 17-40 was a no brainier for me.
When I had the 17-40, I found myself longing for a 16-35 when I just wanted to use it indoors as an all-purpose lens.
Otherwise didn't feel the urge. But then I didn't have a body good as a 5D3 so for you I think the 17-40 would be more than enough

In that case, the 17-40L is a perfect match unless you really need/want the 2.8.
Here's another from the 17-40L, I think it handles distortion quite well.


Downtown rooftop expositions.
Thanks for all the replies.
And yes, I think the next lens is 17-40L.
Only worry for me, was concert shots. But last friday had an honored to take shot shots of Eric Dover (Slash´s Snakepit singer), Eric Brittingham (Cinderella), Ryan Roxie (Alice Cooper) just to mention a few on stage, and my 35mm L was wide enough for those close-ups. If and when I need more light 
So 17-40 it will gonna be.
And by the way, fantastic photos in this thread.









