Re. The Canon 24-70 and 24-105, these have very strong field curvature, which can show up as a noticeable drop off in sharpness at the extreme corners, even when well stopped down. Personally, I would not use these lenses for architecture or landscapes unless I was sure that I'd always be cropping out the extreme corners. For portraits, weddings, events, photojournalism, that would be another matter. However, this will depend upon how much the photos will be enlarged.