I almost always recommend
this link to folks who are looking for ultrawide lenses. There are side-by-side comparison images for you to examine. My personal experience (having owned BOTH Tokina 11-16 and Canon 10-22 at one point) is consistent with Juza's observations.
Ultrawide lenses are used for special effects and landscapes. As such, bokeh is hardly important. Flaring, on the other hand, is a VERY serious problem and Canon 10-22 is one of the most flare resistant lenses Canon has ever made.
:thumbsup: