[Baron Munchausen]

Actually, the comparison of a particle beam to any other 'matter' projectile is not necessarily accurate. The force of the impact is a combination of the mass and the velocity of the impact. Larger projectiles will of course do more damage at the same speed, but practical considerations of technology (and scale) might make it much easier to increase the total energy of impact by using a particle beam to get extremely high velocity with a tiny mass. Accelerating larger 'solid' projectiles to produce equivalent energies might be much more difficult, and the 'cost effectiveness' curve might be very different.