A TVS diode with snapback behaviour has different semiconductor structure than a "regular" TVS.
Regular TVS uses a P-N junction or actually many of those.
Snapback TVS is structured almost like a thyristor or SCR. So at certain breakdown voltage it becomes conductive and the voltage drops. It can actually drop quite far in "deep snapback" TVS. Then it maintains the holding voltage for the surge duration. Of course you cannot use it as a thyristor due to its power rating.
So obviously the snapback TVS is better suited for low voltage system protection as it maintains lower voltage after the overvoltage event triggers it.
Unfortunately I cannot say if your "device" will survive a momentary 11V spike as I do not know what the device characteristics are and what are you trying to protect it from.
