I'm not entirely sure which one had farther reaching effects. The Congress of Vienna (1815) was called to restore the balance of power in Europe and to restore the French Monarchy (undo the Revolution). The congress also divided up German and Italian states that Napoleon had unified. This angered many people and gave way to the Revolutions of 1848 and other nationalist uprisings all across Europe that embodied liberal ideals. In 1871, both Germany and Italy unified because of the nationalist sentiments that the Congress of Vienna instilled. So, the French Revolution and Napoleonic wars changed the sociopolitical makeup of Europe and gave birth to 2 new unified countries as well as nationalism, which STILL plays a huge role in world politics.

The First World War gave rise to global governance, the idea of collective security, the mechanization of warfare, and the Treaty of Versailles which economically crippled Germany, humiliated its people, and gave rise to ultranationalism in the form of the Nazis.

Bottom line, both of these events changed the world in no small way and I can not honestly say which event changed Europe and the world's politics and future history more dramatically. I guess it's up to your opinion.