I’d go with the Canon if the price isn’t a consideration. I’m sure you’ve considered most of these points already… It has less distortion than the Sigma. Its supposedly sharper too. f/3.5-4.5 on the Canon vs f/4- f/5.6 on the Sigma can’t be ignored either. I’ve borrowed the 10-22 a few times and it is next on my shopping list. I don’t think the Sigma has FTM focusing either. Its a really nice lens.
I haven’t heard much about the Tokina 11-16, as its just come out. Constant f/2.8 is nice, but you pay for it with a very limited focal range. I’m not sure how it performs distortion wise. One to consider if you shoot a lot in very low light. Though the ultra wides are pretty tolerant to handholding at low shutter speeds anyway…
Canon would be my pick! I don’t know anyone who has one who wishes they’d bought the Sigma…