Looking at the stat cards, they both use the same ji, which is an armor piercing weapon. The difference in armor only matters for the non-ap component of the weapon strength which is only around 50% in the case of the ji. They also have similar melee defense so the only other advantage the heavy infantry have in a melee infantry head to head is their higher attack accuracy.
@LordObsidian1250 it's kind of a shame, really. While both units use the same weapons, you'd expect Tier 3 heavy units or Tier 2 professional standing troops to have higher attack and defense skill apart from only being able to adopt advanced formations.
