EXCELLENT DEPTH OF FIELD (BOKEH)
In portraiture, one of the most important elements to have is a healthy amount of subject/background separation. This is also called a shallow depth of field or ‘bokeh’. Most 24-70mm f/2.8 lenses provide nice bokeh, thanks to the fact that they have a reasonably wide aperture (throughout the focal length!).
I personally try to shoot at maximum zoom, as this is where the bokeh effect is at its best, and your subject fills the frame nicely.