They both have the power to heal. Sakura has the power to smash things by sending chakra to her hands. Don’t think that Katara is weak. People say that she need water near by in order to fight but she a lot stronger than you think. She can pull water out of the air and plants and she also knows how to blood bend. Blood bending is a form of controlling some one blood. This allows you to controll their body and movement. You can also extract the blood from their body. So Katara can’t lose.