Sorry to sound like KR but I limited the size to 1024 on purpose. I was not testing sharpness, including in the corners, where sharpness is not for given, even at f/11 but see also (2) below. There is much more to a lens than sharpness.
The 24-105 is sometimes bashed as a lens having low contrast, blah colors; somebody was claiming "too much clarity in dull light" (I will test that, too), and all that sort of nonsense. It is NOT true that all lenses perform similarly at f/11. Here are a dew differences:
1. Color: for example, the 100L is much more colorful (not always in a good way) than the 135L. Lenses like the 50/1.8 and the 50/1.4 are really dull in terms of color rendition compared to modern and not so modern L lenses. Even in the samples I posted, you can see that the 35L is slightly cooler than the zoom. L lenses can render reds very differently; the newer ones are much warmer, in my experience.
2. Contrast: Some lenses (the worst I have seen is the 18-55 IS) have noticeably low contrast like a haze over the whole image – gray blacks but not only that. The 135L has lower contrast in the highlights than the 100L but deep blacks. There are also micro-contrast differences among lenses, visible even at this resolution.
3. "DOF" and brightness (T-stop as opposed to F-stop). You cannot see that at 1024 pixels but the landscape shots show something very interesting, which I will investigate further. The 35L is 0.4 stops brighter (in both cases) and has more "DOF" (measured with very small CoC) than the zoom. I will post crops later. They are both focused where the yellow flowers end and the trees start but the background in the corners is (a) very sharp with the prime and (b) starts to get fuzzy with the zoom, still within the accepted DOF range though, after all, I focused past the hyperfocal distance. Now, (b) is expected but I am surprised by (a). In contrast, the lower (close) corners do not differ too much by sharpness.
4. (EDIT) And, of course, flare (and this is connected to (2)), in which the 24-105 is an average performer bit often good enough. Flare can and does affect contrast in some situations however.
Yes, those shots are in good light, and I did say so.