Solar Energy: Do PV cells in series or parallel give better maximum electrical power?

If the panels are the same voltage and wattage output, there is no difference- power is watts- which volts times amps.  Think of them like flashlight cells.

One thing though- a higher system voltage is less prone to issues of wire resistance and voltage drops that can be a real problem with long wire runs at 12 volts.  A good reason to run higher Buss voltages.

If the panels are different ratings, wiring them in parallel is the best option.  If they are in series, you are limited in current output by the lowest current producing panel.  In series-voltage is additive, in parallel -current is additive.