In my opinion if you own a crop sensor you need to have an UWA lens. Believe me, i tried to get out of buying one. Went to a 17-55 and thought I could have the best of both worlds. One a crop sensor 17MM is just not wide enough (for me) for interior shots and landscape / travel photography / cityscape, etc.
I have an 11-16 Tokina and think it's one of the best UWA lenses every produced. I wouldn't mind owning a Canon 10-22 though, but love my Tok.
All opinions expressed by me are my own opinions & do not represent the opinions in any way of my employers.