Well, I don't know... I think at the same time you can get: King of the Undead's Cloak, Cursed Armor, and, for example, a Sniper's Bow... and then compare... :(
Cursed Armor.
For 50 turns, all opponents are affected by the spells: Slow, Curse, Weakness, and Misfortune.
Sniper's Bow.
Ranged units can attack as long as there is an enemy creature nearby. No problem with long distances.
Which is better? It depends on the player. If you have a lot of archers, take the bow, and if you like to mess with your enemies, take the armor!
P.S. I would still take the armor!