I love both fandoms, But no. I love both Percy and Harry equally and am a part of both fandoms. If I'm going by pure fact, Harry would win. I mean, Look. Harry could, If he chose to, Use the Avada Kedavra spell and kill Percy, Though that's not something Harry would do. However, Harry has any number of spells at his disposal, While Percy just has Anaklusmos/ Riptide and the powers of water.
Depending on the circumstances, Percy could possibly overpower him, But in a natural sense, Harry would be the winner of the battle.