I remember seeing something a few years back that made the case that Ship to Ship space battles would be fought by AI Drones. Due to the extreme 3D maneuverability of small craft with thrusters , humans wouldn't stand a chance against machines capable of making advanced tactical calculations in milliseconds.
Whether or not projectiles would trump high powered energy weapons would depend on the sorts of shielding and materials in use to create spacecraft with.
However, a rapid fire rail gun does seem like it would be ideal for close quarters combat and require less energy to penetrate shielding and armor.
But perhaps more exotic ammo than slugs would be more useful, imagine a round that on impact would release rapidly replicating nano-bots that eat through the ship's hull until there was no ship or deliver an EMP to disable the systems.