>>3323204Not as much light or subject separation. Kit lenses tend to have an aperture like f3.5-5.6 so they're not great in low light or for getting blurry background (bokeh) from your subjects. You'd have to try pretty hard to get anything pleasing out of them for subject separation.
Prime lenses tend to excel at allowing in more light and bokeh. Higher end zooms will have either allow in more light like starting at f2.8 or they'll have a fixed aperture that doesn't darken as you zoom in like kit lenses do. The aperture remains the same throughout the zoom range which is good for video as you don't need to constantly adjust exposure as you zoom in.
