If you are a person who actually uses the full range of gears on your bike (many don't), more gears can be a benefit. You needn't limit yourself to 9 gears, you can run up to 11 on an HG hub (or even 12 with aftermarket cassettes). Choose a gear range suitable for the terrain in your area. For myself, I also ride motorcycles, and ride my bicycles like motorcycles, I always shift down as I come to a stop, and shift up after I start, and as I pick up speed. More gears makes it easier to find the best cadence for a particular speed and terrain, and this increases my pedaling efficiency.