From: Alan Inness <intek@escape.ca>

Peter, A switching power supply does not have the heavy transformer that a
linear PS has. It achieves the transformation by electronic switching
(simplified).
Consequently they are much lighter and usually more efficient, myself, I
prefer a linear PS.
I have used the switching type, but they seem more prone to damage from
voltage spikes, unless precautions are taken to filter the supply.
p.s. The power supply in your computer is a switching type.
Al Inness