One other thought regarding prop efficiency (stating the obvious, but since the salesperson brought it up . . .)
Fixed props are more efficient than feathering props for propelling the boat forward while motoring. If one has a power boat, he'll want the most efficient prop for providing forward motion under power.
For sailing vessels, efficiency has to be measured both under sail (weighted heavily since it's a high percentage of our usage) and under power. At least for racing or long distance sailing, the drag question becomes an important factor when considering overall efficiency, yes?