Certainly the adapter issues always a concern. I had special problems with internal reflections using TS-E 17 and 24, but don't recall experiencing it with the 16-35mm...the tilt-shifts may have unique troubles on that part.
But, to answer your question, if size/weight weren't a priority for me then my answer would be a strong "no." There is no other reason, aside from size/weight for me to prefer prefer the Sony FE 16-35mm over the Canon one.
AF performance is equal to 24-70L II on a7R II from my memory, although I usually kept it off for land/cityscape shooting.
OK, there is one weird thing with the lens on a7R II (just odd, not negative). If you switch IS off then the SR app thinks you switched it on and tells you to switch it off. Weird. So, you have to leave IS on during SR app uses. It's weird, but fine. Pictures come out amazing regardless.
Thanks for the feedback David! I definitely value your expertise in the realm of landscapes/architecture!
I'll probably add the lens to my kit again one day...probably not till the latter end of the year when more paid works starts rolling in again...The Canon can be had for quite a bit less than the Sony 16-35 F4, and is much cheaper than the 2.8 versions....but I'm broke from the a9 purchase since I decided to keep the rx1rII lol.