Iron Bane or Destruction, which is better?

[Inigo Montoya]

My understanding of the pros and cons:
Destruction, if you want to destroy armor - limited to AOE of 6, but no need to strike a hit.
Iron Bane, if you want to hit the entire battlefield - the armor is rusty, but not broken. Everytime for the next four rounds of combat that the attack "hits" after damage is assessed vs protection, then the armor has a 50/50 chance of becoming broken and dropping to 0 protection (with exceptions for magical armor, natural protection, etc). Note Iron Bane affects your own units.