I haven't used either lens, but I will say that your link is not a good comparison which may be why you're a bit confused over what the review says.


These are 100% crops from camera of very different resolutions and sensor sizes. You really need to compare a lens on the same camera to get a fair comparison, but that option isn't available for teh 24-70 and 17-55 since the 24-70 was only tested on FF.


To illustrate my point, check out how the 70-300 tests against itself on the 40D and 1Ds MkIII


http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=358&Camera=453&Sample=0&am p;FLI=4&API=1&LensComp=358&CameraComp= 452&SampleComp=0&FLIComp=4&APIComp=0


Crop cameras, especially the 7D have much higher pixel densities and so are more demanding on a lens at 100%. This is part of why full frame images can be so much sharper, because there is so much more space (and glass) feeding each pixel even at high resolutions.


As a side note, see the following quote about the accuracy of the ISO charts here: http://www.the-digital-picture.com/Help/ISO-12233.aspx


"For the most part, I find the results to be very indicative of the image quality of the lens being tested and
the comparisons work very well - the results are even better than I had hoped for.
However, I'm not totally satisfied with the Canon EF-S 17-55mm f/2.8 IS USM Lens
results - the 17-55 under-performed in the comparison tool images in my opinion"



Back to your lens choice briefly, I used a 24-105 on my 40D and I would not have been happy if that was my widest lens. I also had a 10-22 which I used for landscapes and even indoor sometimes.