24-105 L versus 24-70 L lens
24-70II is sharper and have better contrast. 24-105 have longer reach and IS. The down side, 24-70II is heavier and more expensive.
I had them both for some times, but decided to sold my 24-105 as I did not need its reach (I have 70-200) and I prefer to shoot wide open at 2.8.
Oh, did I mention 24-70II's bokeh?