Because the Mars can reload itself and continue fighting fire without having to land, stop, and get refilled, it can put more water/retardant mix on a fire in an hour than ANY OTHER AIRCRAFT, bar none.
This is especially true when there is a large lake, wide river, or the ocean near a wildfire.
Sure, the 747 can drop more in one pass, but it GETS only ONE pass.
Don’t kid yourself, 25 tons of water is a LOT of water!
When the doors open, the aircraft seems to climb 2000 feet in 15 seconds as the water leaves the tanks. It is a sight to behold indeed!