What carmusic is trying to say is that switching power supplies can be from 85 to 98% efficient. The LM323 based supply is low noise, linear. Depending on what's it's asked to deliver, determines it's efficiency. Switching regulators typically use the collapse of inductors to regulate. The inductors are pulsed with a varying in time DC signal, thus trying to not waste energy.
If you think about a 31 V unregulated supply asked to provide 1 V at 10 Amps, (31 V - 1V) * 10 is 300 Watts. This is going as heat. If the same supply is asked to deliver 0.1 A, then (31 V - 1V) * 0.1 A; then 30 W is wasted as heat. Typically a little less, but you get the idea.
For a bench supply, linear isn't necessarily bad, but it will be BIG.