True, it is a tough choice. I would not fault anyone for either choice.
As for me, I will say my 24-105 f/4 essentially sat on a shelf after I bought my 24-70 II. I intentionally took it on a trip just to use it. But could have just as easily taken the 24-70 II.
For me it gots down to the extra dof control, extra light while maintaining shutter speed, distortion, and more pics that "pop" IMO. I do think there is an AF advantage as well.
I already have a complete set of 82 mm filters. So that is moot for me.
But both good if not great lenses. I am looking forward to see what the 24-105 II offers in terms of IQ.