Center sharpness, extreme border sharpness, and CA at 11mm are shown here in this test. With regards to center sharpness at 11mm, I found the Tokina to resolve a little more detail at matching apertures. At the borders to extreme borders, the Tokina is magnificent and the Canon cannot compete. In terms of CA and color fringing (lateral CA/purple-green), for all intents and purposes, these two lenses are comparable. They are "average" performers, at best, in this category.

Concerning contrast, both lenses deliver very good-to-excellent contrast reproduction, although if pressed, I'd give the slight nod to the Canon here. But both are excellent. Also, I don't show the 16mm performance of these two lenses, but note that the Tokina is sharper at 16mm than it is at 11mm, if that is of any help. The Canon at 16mm is at f4 wide open, so there is a whole stop between them at 16mm. And as for barrel distortion, while not shown, my conclusion is that the Canon is slightly better here than the Tokina, although both perform quite well for the UWA class.