tokina 11-16mm f2.8

I've had my D5000 for a few years now and would like a couple of new lenses, which after some reading I've decided on these two. I already have the Nikon 55-200, which I use for wildlife and trips to the zoo, plus occasionally when I go to the stock car racing. I love the lens but I would like...

Has anyone experience with either or both of these Tokina lenses? Or should I consider something else? (like Sigma 8-16mm) I never owned wide lens so I'm unable to tell the difference which one will be better 11-16 or 11-20? Please let me know your thought! Help.....help....help. Thanks Eve