I raced a C25 for many years. Rolling up the jib in light air reduces sail area at a time when you need as much sail area as you can get. In light-to-moderate winds, I sailed wing-and-wing with a whisker pole extending the genoa to the maximum. Some handicapping systems limit the length of the whisker pole, and others do not. If you're just sailing casually, it doesn't matter, but if you're racing, you'll need to know whether the length of pole is limited by the handicapping system used in your venue. The fully extended whisker pole prevents the genoa from collapsing, and keeps it driving the boat downwind in light air.
+1. If you're a cruiser, and you're "spinnaker averse", just pole out the jib with a whisker pole.