Well, Baron, modern physicists believe that energy is transmitted by particles (i.e., photons for light, various quarks for strong & weak nuclear forces, electrons for electromagnetism; still looking for the gravity particle). Therefore, the energy stream/energy pulse weapons in SE4 would HAVE to use particles somehow; we can justify the name by claiming that the weapon fires a "stream" or "pulse" of (thousands/millions/billions/etc.) of particles, which act like an energy wave, which then damages the target (well, if it hits...).
The mass driver (Depleted Uranium Cannon) fires a single particle, which (hopefully) impacts on a target and transfers kinetic energy via a classic collision interaction. Even though the damage is due to transfer of kinetic energy, I think we can all agree that the mass driver shouldn't be an energy weapon, since the mechanism for carrying the kinetic energy is a large mass (compared to atoms; the projectile should be MUCH smaller than a ship
), and behaves like a particle.