Don't you love how people disregard data so quickly if it opposes their own narrow views.
What vgchartz does is amazing and ioi getting us this data every week is great but their is no argument amongst any corporation, organization or knowledgeable individual that NPD's data for the United States is far far more accurate than vgchartz, especially on months like this that have such massive fluctuations in sales. NPD has massive resources when it comes to gathering data and vgchartz as of today simply can not compete with them.
Go back and look at last month when the PS3 was undertracked at vgchartz compared to NPD and see how quickly some members tunes have changed.