I never got a straight answer for it. What is it? Does it need to low or high? Explain someone please
Falloff is the amount of explosive power lost per tile.
An explosion with a power of 500 and falloff of 50 will spread ten tiles, being 50 power less per tile.
What forest said, falloff essentially determines how much area the explosion will cover, while power determines the damage it will do. Having a bomb with very low falloff will make it spread to a large area, provided it has a decent amount of power too.
On the other hand, the same bomb with a high falloff will not damage the surroundings as much, though at the center tile of the explosion the damage done will be identical.