I've heard a lot of varying statements on the differences between spherical and elliptical styli.  What are the real differences, and the reasoning behind them?

As you may know, the physical difference between a spherical and elliptical stylus is the shape of the diamond.  An elliptical diamond allows for more detailed sound quality, as it fits better within the groove and therefore has more contact area with the groove itself.  Elliptical diamonds penetrate the groove walls further, extracting more intricate detail, especially in the high end, than is possible with a spherical diamond.  It is commonly misrepresented that elliptical styli cause more wear than spherical styli.  In fact, spherical styli, since they have a smaller contact area and more pressure, cause more immediate wear than elliptical styli, but in a smaller area of the groove itself.  Elliptical styli, since they have more weight distribution amongst a larger contact area, will wear the groove slower, but will wear more of the groove over repeated backcueing.  So to answer the question, an elliptical stylus will cause more wear, but for a different reason than is commonly assumed.  Ortofon's DJ cartridges use a modified elliptical stylus, known as "special elliptical" which can stand up to heavy backcueing, unlike traditional elliptical styli.