17-40 but thinking of getting the 16-35. It's great shooting wide on a FF camera
17-40 f/4L for me, too.
I don't know why you'd get the 16-35 if you already have the 17-40, it won't make much of a difference as far as field of view is concerned. It might help with indoor shots if you're talking about the 1 stop and IS difference.