Why is there so much difference between sony psp shipments and VGC data?

sony total psp shipments ->61.5 m http://news.vgchartz.com/news.php?id=80014&mp=1 

VGChartz Hardware data for the period 05th Dec 2004 to 03rd Apr 2010: 57,632,824 

http://vgchartz.com/hwtable.php?cons[]=PSP®[]=Total&start=38333&end=40272

But nintendo ds shipment ->128.89m  http://news.vgchartz.com/news.php?id=79945

VGChartz Hardware data for the period 21st Nov 2004 to 03rd Apr 2010: 127,966,736

http://vgchartz.com/hwtable.php?cons[]=DS®[]=Total&start=38319&end=40272

This may be an interesting topic. I don't know. All I see in the OP are way too many links for me to even consider clicking. Summarize the point you are trying to make in your OP. I have an extremely short attention span and it would really--

boobs.

*goes to look for boobs*

Prior to April 1, 2007, Sony reported units manufactured as "sold".  This lead to large discrepencies between Sony's reported figures and figures reported as sold to consumers by all retail tracking firms including NPD, GfK-Chart Track, Famitsu and as you've noted, VGC.

After that date, Sony began using the idnustry standard practive of reporting units "sold to retail" as "sold".  This brings reported figures much closer to those reported by the retail tracking forms such as those I listed above.

in this article http://news.vgchartz.com/news.php?id=80014&mp=1 says that 61.5m are shipment sales because Cumulative Production Shipments(Until March 2007)+LTD Unit Sales(Since April 2007)=63.2m http://www.neogaf.com/forum/showthread.php?t=395262 

hmm something seems off, perhaps VGchartz finds it difficult to track smaller countries

That's the difference between VGC only accounting for units shipped prior to April 1, 2007 and Sony still including those manufactured units for their cumulative totals. A production shipment is a units manufactured and shipped to their stocking warehouses.