The Canon EF-S 17-85mm clearly exhibits greater geometric distortion and coloured fringing than the EF 24-105mm when both lenses are zoomed-out to their widest positions. Stopping down the former improves the sharpness slightly, but the colour remains.

Zoom both lenses into telephoto though and the story changes. Here the EF-S 17-85mm delivers much sharper results in the far corners than the EF 24-105mm; indeed the latter is quite soft in the corners even at f8.

Note: crop details taken from the same chart which appear smaller here are due to them being captured with lower resolution cameras and / or a lens which couldn't focus as close to the chart. In each case though, the crop still represents the extreme left corner of each camera's frame.