Neither version of Darkside can win.
Reason 1: the Omega beams dont kill you if you are a fixture in your universe. But Preacherverse is not part of normal vertigo univers so it may not work. The omega beams may work on him. Other then that, i dont know how he would destroy him.
Reason 2: Newest version of Darkside cant seem to kill anyone with his Omega Beams, I dont see how he could kill SOK.