Which is better: Zamzam water or Kawthar water, and what is the reason for naming each of them as such?

Al-Kawthar is a river in Paradise, named so due to the abundance of its water and its goodness. Zamzam is a well in this world, named so for various reasons, among them Hajar's saying to the water: "Zam Zam" (gather, gather) for it to collect. There are other accounts for its naming, referring to preventing the water from flowing or the sound of the water. It has many other names. It is not possible to compare Zamzam water with Al-Kawthar water, as the former is from this world and the latter is from Paradise, and what is in Paradise far exceeds what is in this world. As for what is mentioned in some narrations that Zamzam is from Paradise, it means likening its water to the water of Paradise in terms of the abundance of goodness and blessing.