Paris & Rome have roughly the same population, just over 2 million people. Both cities are internationally famous and attract high levels of tourism as well as being business and administrative centres. Paris has a further ten million people in its suburbs, whereas Rome has only a further 2 million.
Rome has many more priceless monuments and the Vatican City, which can seem like a jewel in the crown or a weight round the city’s neck. Both cities are attractive targets for terrorists.