I like the 24-70 II better for the below reasons. However, if you have a second body, and you don't need the money, it is nice to have the extra reach. Both are very nice walk around lenses. On the other hand, if you don't have a second body, and you can zoom with your feet, the 24-70 II will soon make you forget the 24-105. So tough to have to choose between two great lenses.
I've had the 24-105 for about a year and a half now. It came as the kit lens for my 5D Mk III. My copy is a very good one, tack sharp and quite fast, as far as I seem to notice. 3 months ago I bought the 24-70 II. It is an outstanding lens, as far as AF response and sharpness are concerned. I think it's better than the 24-105. That being said, is it possible that the 24-105 can still be useful? If I keep it, and don't sell it, to what uses, if any, can the 24-105 be put? Is there anything that I can do with the 24-105 that I can't do with the 24-70 II?!