Does it worth trading in Sigma 10-20 f3.5 for Canon 10-22?

I am pretty much happy with Sigma but have some slight issues with softness mostly on the corners.
I read a magazine review of Canon and they claim it is condirebly sharper than Sigma and Tokina.

There is a website with comparison photos showing center, midframe, and edge shots with a variety of lenses, including the Canon and Sigma UWA's.

http://www.the-digital-picture.com …omp=0&FLIComp=0​&APIComp=0

I checked this website, and the Canon did seem slighly sharper, but it was hard to tell. Of course their results apply only to their copies of the lenses, which may differ from yours.

My opinion is that, unless you are greatly dissatisfied with the Sigma, keep it. Switching to the Canon means giving up the constant 3.5 aperture (if that is important to you.) I say this even though I chose the Canon for myself and am very satisfied with it.

UWA's in general are going to have softning in the corners. I do not think you would see any real difference wiht the Canon.