Abaqus Impact analysis....Differences between dispalcement and Velocity.

Hi Good Afternoon to all, i am modelling a ball penetrating a plate analysis. As i appllied a predifined velocity to BALL to hit the PLATE & i think i can apply displacement BC to BALL to hit the Plate. So  i want to know what r the advantages and disadvantages of using the velocity and displacement as boundary condition for ball to hit the plate.