> NetBSD selected portability. Well, it would be interesting to analyze why it was not selected to be on smartphones and tablets then.
While it may have the widest hardware support of the BSDs, it certainly can't hold a candle to Linux. They always boasted about the large number of supported platforms aka ports, whereas in Linux you would usually count architectures. Then it doesn't look so good: NetBSD supported platforms list contains 10 architectures including one that Linux doesn't support (VAX), Linux supports 27 if I counted correctly.
Even looking at platforms it doesn't look very exciting. Collected under ARM you find many StrongARM, XScale, and ARM9 but not a single Cortex (though there does appear to exist a port to the ARM11 Raspberry Pi).
Without researching it right now I would say that Linux has eclipsed NetBSD in the portability business at least a decade ago.