The following is a list of benefits of the ceramic silicon nitride ball bearing -

• LIGHTER. The ceramic ball is lighter then the steel ball. This means that
  the ball exerts less force outward against the outer race grove as the bearing
  spins. This reduction in outward force reduces the friction and rolling resistance.
  The lighter ball allows the bearing to rev up faster, and uses less energy
  to maintain it speed.

• HARDER. The ceramic ball is harder then the steel ball. This gives you a
  bearing that will last up to 10 times longer then the steel ball bearing
  because it holds it's finish better.

• SMOOTHER. The ceramic ball has smoother surface properties then the
   steel ball. This means
  less friction between the ball and bearing races giving you a faster spinning
  bearing.

• THERMAL. The ceramic ball has better thermal properties then the steel
  ball. The ceramic ball will not heat up like a steel ball. This helps avoid heat
  build up in the bearing, a primary culprit in skate and skateboard bearing
  performance degradation.

• LUBRICATION. The ceramic balls are impervious to oxidation, chemicals,
  and require essentially no lubricant. The bearings are lubricated with a
  very, very small amount of Aral Aralub oil, not a gel or grease.

SOLID CERAMIC. The ceramic balls are solid ceramic silicon nitride. A cheaper
ceramic bearing uses steel balls with a thin ceramic layer.  The elastic and thermal
property difference between steel and ceramic cause the ceramic to split and separate from
the steel portion of the ball on these less expensive look a likes. Avoid this type of
ceramic ball bearing. Ball Bearings

 Ceramic Ball Bearings