Lol. These are the same energy, Antimatter is just slightly faster than fusion, but both generates energy because of E=mc². But the issue with Antimatter is ... How to get it ? ^^. Particles Accelerators ? lawl.
That has not been revealed yet lol, since only real way is to mine it on gaint antimatter planets xD But because it is incredibly fast at releasing it you could use it to get a high enough temperature to warp spacetime, where as Fusion has a lot, but not fast enough.