I believe both will work just as good at the other in vista because both are based off the 975 intel chipset if im not mistaken.
The only differences I can see is that the p5wdh is geared towards home entertainment, while the p5wdg2-ws is designed more for people who need a work station compy.
edit: overclocking on the p5wdh is decent as long as your have a 6600 or higher for a cpu as its fsb is limited to around 400-450(depending on what bios you have)
I dont know how the p5wdg2 oc's though..... google may be helpful