I believe the answer is: A republic is more capable of controlling the effects of factions than a democracy. Can't eliminate factions because you cannot eliminate a person to think.
The basic foundation of democracy is freedom. Because of this, the chance of ideological conflict to happen tend to be high since each individuals tend to have different ideologies and have the freedom to pursue and promote it. But, on the plus side, democracy creates a country where the government cannot become too powerful.
