TweakMDS wrote in post #7780639
Tamron 10-24 is not regarded as the sharpest out of the UWA bunch. Quality-wise, i've seen the most success stories from people with either the Canon 10-22, Tokina 11-16 or Sigma 10-20. Either will do, but it depends on your budget and what you want from a lens.
If you've got the cash, the Canon is excellent. If you're on a budget, the Sigma gives up a little image quality, but is really a bargain at the price. The Tokina is a fine lens (it's actually on my wish list) but that 11-16 focal length gives up a lot of range to the Canon and Siggy, and at the ultra-wide end that's a lot more than it looks like on paper. The fixed aperture of 2.8 is great, but if you don't particularly need that fast of a lens... I have to say the Tok, attractive as it is, remains more of a special-purpose lens. You'll get more versatility and use out of the Canon or Sigma.
With your budget, the Sigma's probably the way to go.