Conventional tokamak based D-T (Deuterium/Tritium) Fusion will produce 17.59 MeV of energy per reaction. Furthermore, the higher the probability that a collision will generate a fusion reaction, the higher the efficiency. Every failed collision means that the energy expended to make them collide (containment and superheating) is wasted. According to Lawson's Criterion, the probability of fusion is determined by two factors: ion density and kinetic energy. The higher the compression rate, the more power output is provided per unit of power input. Tokamak reactors are based on electromagnetic confinement systems, which are limited in how densely the ions can be compressed. Furthermore, other more efficient forms of Fusion (like Proton Cycle Fusion) cannot be used since they require very high ion densities.
A gravitic containment system (using an array of anti-graviton emitters) would have the ability to generate a lot more compression with less energy expenditure. Since gravitons more directly react with matter than EM fields do, they more effectively control the plasma. This increased ion density not only increases reactor efficiency, but allows the more efficient Proton cycle Fusion that is used by stars (providing 25 MeV - 142% more power). Since graviton systems wouldn't require complex toroids, but simple spheres, they are also a lot smaller - allowing more reactors to fit in the same space. The gravitic system could also pull out heavy waste matter using graviton systems. Lastly, the gravitic system would allow the reactors to control compression levels in gradients. This allows the reactors to control power output without shutting down reactors therefore saving the ignition power.
Proton Cycle Fusion not only produces more power from the same fuel, but runs on simpler fuel. While D-T Fusion requires one to produce deuterium (relatively easy) and Tritium (hard to produce, and harder to store since its radioactive), Proton Cycle Fusion uses simple Hydrogen. This means no energy expended in pre-processing hydrogen and only one fuel storage tank. Additionally, this cycle outputs only Beta and Gamma particles, whereas D-T Fusion outputs neutrons as well that can pollute the plasma. This reaction type allows more power to be generated with less mass of fuel, it also provides less use of power in the reactor/fuel system.
The anti-graviton array also allows the system to dynamically to control the containment field. This allows the system to siphon the heavier waste molecules from the plasma and use them for thrust or additional power generation (cooling the plasma). This allows the reactor to run at the optimal level with as little waste material in the plasma as possible.
Since this system can control both the compression and reaction volume/mass, they can operate with very little output up to very high output levels and be simply changed. This allows all reactors to remain on at all times, but work at say 0.01% output when the system doesn't want to burn fuel. This avoids the amount of time and massive energy required to ignite a fusion reactor. This allows a graduated power output level allowing the reactor array to output the optimal power levels, leading to maximum level of efficiency.
Combining the more efficient reaction mechanisms with the massively increased reactive capacities used in this system, power output and efficiency will be increased by several times. GRC Reactors will provide both large and small ships with the power they need for exercises implausible with D-T Tokamak Reactors.