The only problem with a Spot is in Australia you need a PLB for a flight over 50nm unless you have one affixed to the aircraft.
Yep, over here you need and ELBA full stop, so not much different.
Based on the high failure rate of ELBA's to actually do their job there's a few pilots I know of that place more faith in Spot, even though they have a serviceable ELBA.
An ELBA or PLB is only activated after the event. The ELBA should be automatic but so often the aerial or aerial connection is damaged to the extent it doesn't transmit effectively. With the PLB you need to be conscious to activate it.
Spot is broadcasting right up till the event thus giving an accurate position without any reliance on there needing to be a method of activation.