Sounds like you might have made your choice-- but just to chime in:
I've tested the 10-22 and own the 11-16. I needed the constant, fast aperture, so the 11-16 wasn't a hard choice. It is definitely prone to flare, though I haven't had a huge CA problem (seems trivial compared, to say, my 85 f1.8 ). The short focal range is the biggest drawback; unless you're planning to shoot wide shots for an extended period, it can be tedious switching lenses or carrying two bodies.
The extra reach of the 10-22 not only gives you one more degree on the wide end (which is bigger than it seems at wide angles-- a 9% gain over the Tokina) and the reach at 22 gets you all the way to a classic 35mm perspective. In other words, it can shift between UW and the more intimate but still moderately wide framing that many traditional journalists and street photographers used. The Tokina is always a bit too short when you need to make such a transition-- which is somewhat frequently, for me.
For you, it sounds like tripod-mounted landscape work is the name of the game, so you might be less hassled by lens changes. But if you'll be using the lens for other applications, the focal range is a consideration.
Otherwise, the lenses are about equal in sharpness, at least in my eyes. Canon saturation might be a bit better. Tokina has much better build quality-- but the Canon isn't a slouch. Solid but definitely not L-grade.
