Agree with what has been said so far in response to the comparison; this is not a valid test - unless you are aiming to show the 7DII is better.
1: As has been said, the 24-105L at 100mm and f4.5 does not have the same sharpness and contrast as the 70-200ii f2.8 at 100mm at f2.8.
2: You shot the 5DIII at ISO 3200 at 1/125 with a focal length of 100mm, so at best for critical sharpness you were probably dependant on the efficiency of the image stabilisation. You shot the 7DII at ISO 2500 at 1/250 at 100mm, so much less dependant on the IS.
3: You shot the 5DIII at f4.5, the 7DII at f2.8 in relatively dim light, so the 7DII had over twice the (volume) of light reaching the sensor than (the crop area of ) the 5DIII. ( Bearing in mind exposure is calculated on light density, not quantity).
These three points are why you obtained the result you did.
1. I disagree that the 24-105 f/4.5L is any less sharp than the 70-200 f2.8L (Mark I) at 100mm. http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=355&Camera=453&Sample=0&FLI=5&API=1&LensComp=103&CameraComp=453&SampleComp=0&FLIComp=2&APIComp=0
2 & 3. And yes, in my initial post I noted that I would have preferred to compare the same lenses side by side, with the same settings. This was more of an "after the fact" attempt to compare images, as I wasnt planning this review during the shoot. In a next step, I will definitely be comparing the same lenses with the same camera settings.
Thanks for the input! It definitely helps with future videos and reviews, so I can provide better data.
Two apologise; just re read this and I see I didn't realise you were using the mki version of the 70-200/2.8 IS. Agreed, in the centre at these apertures the 24-105 is equal, possibly a tad better.
Also ignore my point 3, I think I must have been working on you having a longer focal length at f2.8. (The longer the lens the greater the volume
of light that passes for a given aperture. So in this situation you would have been much better to use the 5DIII with the 70-200 @200, @f2.8, because although exposure
remains the same, you would have had a much greater volume
of light in your shot.)
I think we are really looking at point 2. 1/125 at 100 mm is risky for critical sharpness, 1/250 is much safer.