If the experienced player were to go at it on Emperor, the game would not actually become harder for BOTH players, as the AI would get quite a few advantages. With a big skill gap, you may have a new player, about Chieftain level, going up against their friend, who usually plays on Emperor. If one player is on a higher difficulty, this is usually to level the playing field, as one is more experienced and would run away with the game on equal footing. On King and higher difficulties, the AI starts explicitly recieving bonuses to their own play. For what it's worth, the AI plays on Chieftain, so there's that.
So a player on Prince would be significantly disadvantaged over an opponent on Settler. Even then, IIRC, Settler-Prince only affect the player. It gets a little complicated if you add bots to the equation.
