Tol Barad, granting PvE daily quests... plus the equivalent of VoA... to the winning side.
That should motivate the PvE players, on both factions.

Depends on the realm I suppose.
I doubt I'd transfer factions or servers, now that I'm established.
But if I were picking a new server, I'd want to be on the side with 40-45% of the total population... close to 50%, so we're not automatically overrun in world stuff, but the lower population side for faster queues and greater chance of all toons getting into TB etc.