Looks like the 24-105 II sacrificed sharpness in the center for slightly better edge performance. I will also say, I see less CA, and better distortion control. While both can be corrected in Post, I am a believer that everything done in post has some affect on IQ. Also, I was never impressed with the IS on V1. If that is truly up to 4 stops, that would be a huge improvement.

All that said, my 24-70 II isn't going anywhere. That is my general purpose zoom and I am loving the images I get from it.