Comparison between linear regulator and switching regulator for this purpose:
Linear :
- Output Power - 6.3W
- Drawn Power - 12.6W
- Efficiency - 41%
- Stability - Great, depends on design, but almost never fails.
- EMI - None
- Audible Hum - Depends on construction, mostly from mechanical vibrations of the transformer.
Switching:
- Output Power - 6.3W
- Drawn Power - 8.4W
- Efficiency - 75% Depends on design but rarely above 90%
- Stability - depends on design, in general more unstable than linear regulators. Certain problems arise when left without load, especially in this design. Sometimes a dummy load can be used. Again depends on design.
- EMI - depends on design, tends to be high, and hard to supress. May introduce hum in the mains, I've had such problems with cheap phone chargers.
- Audible Hum - Depends on design, sometimes the switching frequency is in the upper end of the audio spectrum, and can be heard by children and young people.
