First for me is far more logical to compare official numbers instead VGHCHZ tracked numbers that are constantly getting adjusted, also its far more easier to predict and track Switch shipped numbers because we are getting offciall numbers for them regular basis. Second, I dont think its big difference when we comparing PSP numbers in any case because PSP is not producing and selling any more in any case, with official ship numbers for Switch, because like I wrote, ship numbers at end eaquels sold numbers in any case, like you can see for instance on examples of Wii and DS from link down and VGHCHZ numbers for those consoles (its same number). Also, keep in mind that shipped numbers means sold to retailers consoles, so Nintendo sold them in any case.
Once more; I know what shipped means, the point is that this was never specified.
In some cases, the difference can be vast, the Wii U was selling on its initial shipment one whole year after release. I know, I know, this isn't the Wii U, but it suggest that shipped numbers don't tell us what we need to know short term. How many units that end up in customer hands, and at which pace, tells us of the market's movement, retail orders do not in nearly the same capacity.
End of 2016 hardware sales:
Wii U: 15 million. PS4: 54 million. One: 30 million. 3DS: 64.8 million. PSVita: 15.2 million.