Siggy 10-20 vs 12-24?

Just wondering what your thoughts b/t the Sigma 10-20 vs the Sigma 12-24. Is the latter one an older model?

Sigma 10-20 are made for a crop body and Sigma 12-24 are made for the full frame.
Sigma 10-20 is newer than Sigma 12-24.

also the 12-24 has a protruding lens so rear filters only unless you use their weird cap that can have a filter, but causes vignetting

I have the 12-24 and have to say that i love it... its a super lens... no ye cant really use filters but that really isnt a problem when ye have photshop and bracketing at your disposal. It has absolutely no barrel distotion and is well built and focusing is quick. The only thing is that its not amazingly sharp but again a little extra unsharpmask and its solved. It has got me out of a lot of corners with interior architecture shots on the 20D where the Canon 17-40 wasnt enough. On my new 5D its unreal how wide it is. A friend has the 10-20 and has a lot of praise for it but without having ever used it I cant compare the 2.

Richie