Anyone with the new version of the Tokina 11-16? I haven't given it a fair shot, but have seen more "popping" pictures from the Tokina than the Canon. The new Sigma 8-16 gets great reviews, but I'd likely be using a polarizing filter on occasion so that might not be the best choice (with that considered).
PS No offense to the Canon 10-22.
IMO, the IQ differences between the Canon 10-22mm, Tokina 11-16mm, and Sigma 8-16mm are very minor - detectable on rigorous tests (but depending on which parameters you look at, each has strengths and weaknesses), not relevant for real-world shooting.
Basically, the non-IQ features are what should deive your decision. The Sigma offers the widest AoV but is the slowest, the Tokina offers the fastest aperture but is the narrowest AoV and narrowest range, the Canon is in the middle on both.
You mention using a CPL. Be aware that with UWA lenses, a CPL results in uneven polarization - you'll see banding of blue skies, for example. Still has utility, but with limitations.