One practical difference is that 10-22mm, having an angle-of-view equivalent to 16-35mm on a full-35mm-frame camera, is ultra-wide to wide-normal. In "classic" 35mm photography, the angle of view seen by a 35mm lens is quite versatile. When someone posts a poll on popular focal lengths for prime lenses for "full-frame" cameras, 35mm usually seems to win. On our APS-C cameras, the 35mm-equivalent angle-of-view is achieved at 22mm.
I often use my 10-22mm at 22mm, for this wide-normal angle of view. The newer 10-18mm EF-S seems like a wonderful lens, but it zooms from ultra-wide to wide, making it less useful as my only lens for the day.
As for Image Stabilization, well, it is never a bad thing to have, but I have not found myself wishing for it when using my 10-22mm. I do, indeed, find Image Stabilization useful with my 24-105L and 100mm 2.8L Macro lenses. If I shot video, I might well want Image Stabilization in an ultra-wide-angle lens.
When I bought my 10-22mm, the 10-18mm was not yet announced, much less available, so I have not researched the 10-18mm.
As for "pro" advice, well, I am not in the business of photography, but do make evidentiary/forensic/documentary images for official purposes, as part of my duties as a public servant, and strive for "pro" results. I do use my 10-22mm for many of these images; my other "work" lenses being the 100mm f/2.8L Macro IS and 24-105 f/4L IS.
