How the (N)EMP works,
from wikipedia:
The electromagnetic radiation from an explosion (especially nuclear explosions) or an intensely fluctuating magnetic field caused by Compton-recoil electrons and photoelectrons from photons scattered in the materials of the electronic or explosive device or in a surrounding medium. The resulting electric and magnetic fields may couple with electrical/electronic systems to produce damaging current and voltage surges
Now how the DEWs work,
also from Wikipedia.
The primary damage mechanism is mechanical shear, caused by reaction (like a rocket) when the surface of the target is explosively evaporated.
So when we're talking about damage from (N)EMPs and DEWs are we comparing like and like? Seems not. If your airplane is hit by DEW (even in some avionics bus or part of fly-by-wire) there will be no induced voltage that can send damaging currents all through the systems, so no need to worry about your FBW getting knocked out by the single DEW hit.
But explosive evaporation of your aircraft's surface (or even worse underlying structure too) is another matter.