Both combatants make plasma to create the effects that they show.
For Havok, it is the rapid heat change of objects hit with his energy beams that causes them to explode. The Torch is immune to these heat changes and get to far higher temperatures. The Torch could absorb the heat from Havok's attacks if he choose to.
Havok on the hand cannot absorb the Torch's plasma blasts to my knowledge.
As the Torch can also fly for better battlefield positioning, he should win.