The 'power ball' bonus allows, as its name suggests, to destroy all the bricks in one shot without losing points compared to a normal ball. The power ball also gives you the possibility of destroying the penguin or hell skull bricks (in the episodes and levels concerned) by giving you 400 points which the ordinary ball does not allow (both the 400 points and the destruction). When the ball is said to be powerful it is blue, if this option is not active, it is yellow.