With a certain large British airline, on the 300-500 series we used to select the left hand selector to Batt #1 and the right hand to S'by Power, thereby showing up early, any batt charge rate or s'by power anomaly, depending on how often ones head fell backwards to look at the roof.
I carried the same habit across to the NG as it seemed a logical and sensible thing to do, in the absence of the gospel according to SOP.
Otherwise it seems to depend on the preference of the G O F in the left seat, or wherever the switches were left from previous selections.
