The 5 foot difference is "the reach" - pole length extended + average height a man holds the pole. I don't like it but it is how they measure them, especially since when you take into account the that you lose about 25% of that "reach" when you take a few steps away from the building to get the proper angle.
I prefer to get a longer pole than needed (carbon fiber is real nice), that way you do not need to extend the sections all the way so they stay rigid.
Scott, how are ya?