Conclusions are that both the 70-200 and 70-300 are sharper than the 24-105 at 70mm.
There is not much in it at 100mm between the 70-200 and 70-300 although the 70-200 is sharper in the corners (when wide open).
At 200mm the 70-300 wins easily. Given all the 70-300 is a superb lens and one that i sold the 100-400 L for. The IS is great as is the contrast and colour.