Here is what the deal is...
Capacitors smooth the output of a linear supply and a SMPS supply too.
With a linear supply 60Hz or 50Hz mains AC supply the frequency is low and that means large capacitor sizes are needed to smooth the low frequency.
Now.... here's where it gets interesting....
With high frequency power much smaller capacitors are needed for smoothing the output of a SMPS. It has to do with the charge/discharge rate and the rate of the frequency.
SMPS power supplies use roughly ~20kHz up to ~650kHZ switching rates in the SMPS operation and this is present at the output of the SMPS and is smoothed by small capacitors that handle the high frequency switching.
... So when building a 50Hz or 60Hz linear supply large transformers are required for power transfer across the primary and secondary windings.
When building a ~20kHz up to ~650kHZ switching rate SMPS the transformer can be very small because the power transfer across the primary to secondary windings happens more time per second.
I'm not sure to be honest. I have been repairing SMPS since the 80s that was used in monster car amps. So the stuff has been around for a long time and is found in a ton of computer gear. Maybe somebody has the answer here.
O' yes and that is a very good option. To be able to switch out the power supply based on one's budget is a great feature.
