Please don't take what you read on here and what you see in the charts as gospel.
As I put in another thread, I nearly didn't buy the 16-35mm II because of the reviews on Canon Rumors but I went ahead and bought one as I don't see another one coming any time soon. The old buy what you need now rather than waiting for what doesn't exist is good advice.
I nearly didn't buy it because of the poor reviews this site has given it. In practice I have been pleasantly surprised really great lens nice and sharp even at 2.8 at 16mm apart from the very very far corners. Unless I have an exceptional copy.
I haven't used the tokina myself, but it doesn't seem night and day in difference from reading reviews. Its also not as robust and that would worry me when using it professionally, neither is it weather sealed. But it does have slightly better IQ.
I have had it for a week and its right up there with my fav lenses!
Shot I did on wed for a local client Penrith Building Supplies bathroom displays 2014
, on Flickr