I have both a spinnaker pole (12') and a whisker pole (11 - 20') on my P28. I use my whisker pole frequently to pole out the genoa on a broad reach or running wing and wing, and find much greater speed with a more wing-like flatter shape than a rounder shape.
Here is a video of a poled-out genoa at speed:
By all means, get a whisker pole. It is a good introduction to using the spinnaker pole.