In general, normal power factor ballasts are more efficient than high power factor ballasts, typically by a few percent. This is because the high power factor ballasts actually have another electronic processing stage in them, which typically has 1-2 watts loss.
The advantage of the high power factor ballast is that it is much more friendly to the power system in the building and on the utility grid. Power system capacity is limited by the volt-amps provided, not by the watts provided. This is true on the grid, or within a building. For example, no one would consider using normal power factor ballasts for general lighting in a commercial/industrial building, because approximately twice as many circuits (all the wiring, circuit breakers, etc.) would be required. The utility company would also penalize the user for not having a high power factor load.
The task lighting applications are a little different, because they seldom make up the majority of the electrical load in a building, so the system impact is not as great. Many users, and codes (i.e. CA Title 20/24) specify high power ballasts, while others don't.
The difference in input wattage between the normal power factor and high power factor ballasts you are using is a combination of 1-2 watts higher losses in the high power factor designs, and the fact that the existing specific designs do not deliver exactly the same power to each of the rated lamps. The difference in power delivered to the lamps can be seen by comparing the Ballast Factors of the two. The Ballast Factor is relative number corresponding to the power delivered to a given lamp and the light produced by the lamp.