i have used both and i would say the 11-16 is better. The constant/faster aperture is nice. and it is supposed to be a wideangle, i dont see why someone would need to be zoomed in more than 16mm for there go to wideangle.
The 10-22 is not bad at all, by any means. I would say the tokina is better, but the canon is a nice lens aswell. If you dont have the cash for the tokina, and this kid is selling it for that cheap, then get it.