I think I remember someone saying (GCN?) that cadence and gearing preferences may be in large part a matter of genetics. For example, the ratio of fast twitch muscle fibers to slow twitch is genetically determined, and slow twitch dominated leg muscles do better with mashing while fast twitch does better with spinning.
Also, people generally have different cadences for going uphill vs. flat, and some of this is due to the fact that the geometry of the bike--the slope of the hill actually changes the rider's orientation to the bike, effectively raising the handlebars.
I'm a big advocate for try things and see if they work for you rather than listening to someone telling you what should work best for you.