The difference is that 'Allahu Ackbar' is a commonly used phrase throughout the world (both by terrorists and peaceful muslims) and 'Deus Vult' has been out of use for a thousand years. Deus Vult is just a meme brought into circulation by fans of Crusader Kings II and the focus of the game on the crusades, with many fans proclaiming 'DEUS VULT!' online in joking support of their factions Christian Crusades. Polygon is stupid, and so are you, Tony.