As it so happened, I went to a Panamax training session yesterday morning and they hooked up their unit and a Monster unit to a 220 volt overage.
The Panamax shut down and recovered when the 220v was cut off.
The Monster started smoking. Though it shut down and protected the gear, it itself was destroyed in the process and would have to be replaced. (a MAJOR pain)
The Panamax was good to go and it also cuts off from under voltage (brown outs) that will shorten the life of your stuff as well.
The Panamax has patented technology that really works better than it's competetion.