SM
For me it is the zoom range and extra reach of the 24-120.
I prefer the convenience of shooting without having to change lenses.
If you end up in the 50-100mm range, you have to switch between the 24-70 and 70-200. It is easier to just use a lens that has that coverage.
I was at a concert, and the 70-200 was just a bit too tight at the short end, but a 24-70 at the long end would be too short for small group/individuals. So I would have been swapping between lenses all night. Or use 2 bodies with a lens on each.