Wideangle lens for canon 30d

Hi
I have a 30D with a 28-135 which is great, but wish to buy a wide angle lens probably something like the Canon 10-22mm or Sigma 12-24mm.
My question is, which wide angle lens of similar/better quality to those above would you recommend???

Thanks

The 10-20mm Sigma is as good as the Canon and cheaper! that's what I'd go for. Buy it before the end of the year from a UK supplier and you'll get a 3 year warranty with it!

Ian