In my scifi setting I want a broad range of slugthrowers (bullets, smart ammo, grenades,...), exotic weapons (flame/chemthrowers, high tech blades, nano-bots,...), and directed energy weapons (heat rays, blazers, plasma rays, particle beams, plasma weapons). Since the setting is supposed to be hard-scifi, I want the weapons to be plausible from a basic physics and efficiency point of view. The slugthrowers and exotic weapons all fulfil this criteria, i.e. they are optimal for the purpose they are meant to serve.
Directed energy weapons, however, do not generally fulfil that condition. The issue is something Atomic Rockets calls Routledge's Law.
Any interesting battery material for a laser gun would be more usefully deployed as an explosive warhead.
Let me illustrate the issue by going over an example. The weapons energy source is a very small quantity of antimatter annihilated in a chamber made of a gamma-voltaic meta-material. This is the pinnacle of my settings technology, so lower tech societies might use something less energetic, but the issue remains. Assume the chamber has an efficiency of 0.7, and the laser an amazing efficiency of 0.6. Thus the weapon might deliver about 40% of the antimatter's energy to the target.
This sounds pretty decent, until one realizes that just putting the antimatter into a bullet shot at the enemy will deliver almost 100% of the energy. Even worse, modern slugthrowers deliver up to 80% of the chemical energy as kinetic energy to their target.
How can I justify that directed energy weapons are not just specialist tools fore nice applications, but can compete with slugthrowers, so that picking between a slugthrower and a directed energy weapon is more a matter of personal preference than anything else?