Toggle Current Subdivision
Default Shortcut: Alt + V
Menu Path: Subdivision > Toggle Current Subdivision
The Toggle Current Subdivision command will switch an object back and forth between the current subdivision level and the base mesh, allowing you to skip the step of unsubdividing and re-subdividing multiple times in order to compare your subdivided shape at the current level with the base mesh.
Hold the keyboard shortcut down to temporarily toggle between subdivision levels, and then let go to return to the current level.