Ripple suppression
Ripple is a by product of converting AC to DC, and it's characterised by tiny voltage fluctuations that need to be suppressed in order to deliver clean power to your components.
As usual, there are standards for this kind of thing, with the ATX spec stating that ripple shouldn't exceed 120mV evaluated as a peak-to-peak value.
There's good ripple suppression and there's excellent suppression. XFX falls into the good category.