Canon 10-22mm vs Tokina 11-16mm

What are your thoughts on the Canon 10-22mm vs the Tokina 11-16mm?

I am interested in a wide angle lens for my Canon t4i. I know the Tokina has a 2.8 aperture through-out. And the Canon has the range of 3.5-4.5.

Is one lens that much sharper than the other? Is the Canon fast enough for most situations? Which one delivers the best IQ?

Which one would you go for?

Thanks....jane