UDV just means Ultra Durable VGA and refers to the way the printed circuit board is made with a double thickness of copper for the tracks. It means that in theory at least the board can take more punishment, electricly.
I would have thought that the other board would have been the same to be honest as I thought all their boards were to that standard now.
If you can only get the GV-N580D5-15I-B then I wouldn't wait around for the other version unless you are planning to overclock it like mad.