[Mister-T]

Power is power, for the same amount of power

Running pack in serie increase voltage available, so it decrease current load
Running pack in parallel increase overall capacity and discharge rate, Current load will higher on the main output, but this load will be shared between each pack.

Once again, remember, the current is the ennemy,
R x I²,

Summary
Better to run high voltage setup and consequently pack in serie.
Run pack in parallel only when some part of your setup/ driving style does not allow to run HV