Earlier quoted context omitted.
Is that really true in general? I'd say the difference in print start to disappear around 600dpi (dpi/clarity isn't really discernibly different between a 600 dpi print and a 1200dpi print. But up to 600 dpi, I'd say there definitively is a difference)? Granted, with current technology we have single-coloured pixels, so 300 ppi is really 3-900 dpi (or pixel-parts) -- that might have something to do with it?
The dots in your basic 300dpi monochrome laser printer's output are black or white, but on a 300ppi screen you could antialias with grey pixels (or even subpixels as you note), which can boost perceived smoothness/quality a lot. Figure here conveys a difference between PPI and DPI pretty well: http://en.wikipedia.org/wiki/Dots_per_inch#DPI_or_PPI_in_dig...
It's maybe most comparable to the 15" Retina MBP--roughly similar density (220 vs 231), and both are bigger panels you use at a distance.
Just interesting that from a pure spec-wars perspective, raw density isn't one of the dimensions on which the Toughpad is pushing the envelope. Density in its size class, maybe, but not density full-stop.