But you can very well compare them on how they overlap: Is the 70-105 on the 24-105L just "extra" without drawbacks (answer: yes, it even makes the lens sharper @70mm because it's mid-range),
Now that is funny right there! By that logic the 28-300L should be really sharp at 200mm since that is "mid-range". Sorry, but no. Making the lens have a 4.3x zoom range is what keeps it from being as sharp as it could be at 70mm if it had a 2.9x zoom range... Much like giving the 24-70L an f/2.8 aperture is what keeps it from being as sharp as it could be at f/4.
This is basically the same thing I just said above about the 24-70, only difference is that you are turning it into a negative rather than recognizing it as a tradeoff just like you did with the 24-105. You can not have it both ways. If the extra 35mm reach is "bonus" on the 24-105 at the cost of overall IQ at all focal lengths (which it is), then the extra stop of aperture most also be accepted as "bonus" on the 24-70 VC. Otherwise you are just being blatantly biased.
As to which is the sharper lens between the 24-70 VC and 24-105. I already told you I have both and I believe my 24-70 VC to be sharper at F/4. It's not like it would be hard to be sharper than the 24-105 either.... As I showed already even the Tamron 28-75 is sharper at 40mm than the 24-105 according to Photozone.de's testing (as it is at 28 vs 24, and 75 vs 70), and the 24-70VC is sharper than the 28-75.