It will ALL depend on the tolerance you work with. Hood has the correct and most common method. It is FAR easier to restart an ACURATE machine than try and recover after an outage. It will also depend on when you loose power. During a rough cut no problem, during a finish cut?? BIG problem if you have low tolerance finishes say sub .001"
Unless you have a UPS big enough to run the entire CNCmachine you have a very limited time to react AFTER the power shuts down. Usually about 1 sec or less before the energy stored in the CAPS have been used up. This does NOT give you enought time to react and finish a stored position solution before the machine looses position.
NOW even if you have UPS capacity to run the machine during this time as soon as it does shut down and the drives loose power the axis's can DRIFT and loose position unless you have axis brakes to hold it on position(now we really get complicated)
With Hoods method all you have to do is re home and restart somewhere near where you left off.
I would try and only machine during the times that are LEAST likey to have a power outage maybe at night?
Just a thought, (;-) TP