Armor is better than warheads

[dmm]

I rammed an escort equipped with a full engines, an ArmorIII, and a WarheadIII (300 damage, weighs 50 kT) against another ship (a frigate, I think) with a total damage resistance of 305 kT. The outcome surprised me. Both ships were affected equally by the explosion, so both were destroyed. On the other hand, replacing the warhead with 5 more ArmorIIIs and doing the same ramming test resulted in the destruction of the frigate with only armor damage to the escort. So armor is better than warheads for kamikaze ships. Which leads to the question: what are warheads good for?