@scabab
NPD is a professional company with years of experience vs VGChartz is a fan site with not quite as many years of experience.
Now, which is more accurate is a tough answer, as no one really knows since they are estimates. I'm sure NPD is off every once in a while (not saying often, but I'm sure it happens), but they do not publish corrections to the general public.
VGChartz on the other hand may be off more often at first, but publicly displays all corrections. VGChartz is very accurate when it comes to LTD sales. VGChartz also provides a weekly chart where NPD only provides monthly charts. As a final note, VGChartz is far more accurate in hardware estimates than it is in software estimates.
Having a second source of numbers is always a good thing though, so no reason not to want to see them also.
@time question
Right now it is 1:55PM EST, so 4.5 hours to go.