Here is a quantitative followup with various cables and chargers. The results are strange and interesting, and illustrate how mysterious this can all be. Tests are with the tablet discharging at near max I could obtain (through a game demo):
Charger, cable, volts, amps
Samsung N10, Samsung N10, 5.31V, 1.45A
Samsung N10, LG N5, 5.32V, 1.46A
Samsung N10, generic, 5.31V, 1.45A
Samsung N10, Pogo, 5.40V, 1.81A
Generic 2.1A, Samsung N10, 4.96V, 0.78A
Generic 2.1A, LG N5, 4.98V, 1.33A
Generic 2.1A, generic, 4.96V, 0.79A
Generic 2.1A, Pogo, 5.02V, 1.53A
The most surprising is why the Samsung Nexus 10 stock cable performed so poorly on the Generic charger compared to the LG Nexus 5 stock cable on the same generic charger. Makes no sense, so I repeated all the tests and got the same thing again.
It is clear to see the Pogo cable wins by a lot, but is only most effective on the N10 OEM charger.