I'd like to come back to one of the original questions, what the use is of using energy weapons oposed to projectile weapons against fighters/capships in space.
This depends on what shields are. We know shields are not just energy absorbing devices, because they also set of missiles, and ship colissions causes the shields to light up. This means the shields also repel matter.
The most likely form of matter repelling energy field is a highly localised and focused gravity distortion. You'd be warping the space around you so that the resulting gravity force won't let matter in.
If this is the case, in order for such shields to be effective, they have to be so powerful, that before anything has a chance to go through it has to have tremendous kinetic energy. Firing a projectile, giving it so much kinetic energy, would also seriously disrupt the course and speed of your own ship.
Besides, the projectile would be more likely to push the ship and shield away, since there is nothing holding it in place, than actually penetrating the shields.
This means that you have to use either energy weapons or exploding projectiles, like missiles, so you can drain/overload the shield generators.
There is something going against this theory though. With such a shield, it would be near impossible to die because of collision. Surely you could say colliding shields neutralise each other, but asteroids don't have shields.