Southport, Dock Two, Bay Sixteen. . .
See, Lieutenant? Antimatter is only about fifty-percent efficient. Half of the energy from annihilation is released in the form of neutrinos, which don't significantly interact with matter.
If you want to use "inefficiency" to try to talk me out of a pair of antimatter epaulets. . .
. . .you shouldn't be trying to explain things in a room where an antimatter grenade vaporized everything.
Inefficient and dangerous.