Better late than never (was away friday, and don't get to read mail over
the weekend).
Power Factor refers to the relative proportions of resistive and
reactive powers consumed by the device. The more reactive power
consumed, the higher the power factor. Reactive power is consumed when
the impedance of the device is not the same as the impedance of the
power supply.
I know there are integrated circuits which are used in electronic
starters which attempt to provide a low power factor. This may indeed be
the same technology in the "Energy Savings" units, seeing as a 20 watt
tube will always draw 20 watts, the only difference you'll get is the
reactive power dissipated.
So, to summarise, there's probably no difference at all.
Sorry if this is all a bit incomprehensible - it's monday morning (more
or less).
cheers
-steve