I can't answer that but I've owned both, used them on a few different bodies & prefer & kept the 16-36 F 4 L IS in particular for it's better images edge to edge. Way back when I started the change to digital from film I had a 20D and bought the 17-40 and I also bought the first version (and an early 1 at that) of the Sigma 18-200 & frankly the Sigma was so close in the range they both covered that I couldn't tell which I used & nor could others most of the time.
"16-35 worth the difference at $1100 ?"
No, it is not. In real use I doubt you can tell or see any big difference. Let alone a "grand" difference!
Keep in mind most people that do see differences are looking for them. Most people don't look for them.
Thanks for your input. I rented the 16-35 for a few days and came to the realization that I would not use as much as I had
Think I will stick with 24-70 until I travel enough to make it worthwhileto have a dedicated landscape lens.
2/07/2023: New product announcements!EOS R8 EOS R50RF-S55-210mm F5-7.1 IS STMRF24-50mm F4.5-6.3 IS STMRF15-30mm F4.5-6.3 IS STM