And as has been brought up... neither would win.
Darth Nox is immortal through the ghosts that now fill him.
The Wrath is supposedly immortal through the Emperor.
Unless the Emperor knows a way to subvert the ghosts powers, or the ghosts know a way to subvert those of the Emperor... well, it'll just be a bunch of endless combat.
Oh that gives me the most wonderful mental image. Both the Wrath and Nox, realizing they've been swinging their sabers/hurling lightning around for days stop and go: "Ok, time - out, we need a coffee...and why are we fighting again?"