I suppose, as demonstrated, there are two schools of thought here. I know that on Asus boards, they take power from the PSU, even when it is switched off at the switch on the front of the PC .. ie it is powered down.
This feature, which is common on a lot of motherboards that incorporate "wake on ..." functions, which would power up the PC, means that the mobo is still live and the PSU is still supplying power.
This is the reason I prefer to switch off at the back. And as I said, it allows the circuitry within the PSU to smooth out the power spikes when the mains is switched off.