Quote by Karl Hammar: "There are several drawback useing the old
transformer + rectifier design. Of main consern is the current spikes
seen on the power grid when the diodes starts to conduct. Your power
supplier don't like them and that is why we have PFC to make the unit
behave more like a resistor to the power grid."

If PFC stands for Power Factor Correction, using a switching power
supply doesn't free one from using rectification of the mains to power
the switching transistors. The rectifier diodes will also have current
spikes and we are essentially back to square one. With 3 phase power
rectification the current spikes can be greatly reduced as the
rectified voltage output from the rectifier without a smoothing
capacitor never goes below ~85% of peak.

If voltage rectification was such a problem, all devices/appliances
that have to use a DC voltage source would be at blame, which is
clearly not the case. Power Factor Correction enters the equation when
loads having a substantial inductive component exist. This is the case
when certain types of motors are used. Three phase motors do not
produce a significant inductive load if they are well designed. This
is also true of transformers given their primaries are well designed
to keep the magnetising currents at a minimum.

For voltage rectification Power Factor Correction (PFC) is not an
issue. If this is a new issue that older text books about
electricity/electronics did not discuss, please direct me to your
sources of information.