a big advantage of gears is being able to coast and get weight off of your taint. it's nice to be able to
stand up and massage your penis a little after it goes numbs, you know get a little blood moving down there again then move your weight around on your saddle to hopefully keep the numbness away.

oh yeah,
the same gear inches fixed vs. geared is easier fixed.
the benefits of gears come in the form of coasting and gear changes.
flats are easier fixed if you can stay in your comfortable cadence, if not then gears are better.
gears are better on descents and tough climbs.
gears are definately better for urinating to the side while you keep moving.