Which is a better 25% Armour or 25% Damage

[QuaseT]

Armor cap is around 17,500 for 86. Cap armor used (last checked at 81 cap) to decrease taken damage by 80%. This means 1,000 damage at 0 armor is being reduced to 200 damage at 17,500 armor in level 86 maps.
Damage regression is linear meaning everything below 17,500 armor can be converted straight into the reduction multiplier by rules of proportion. For example 8,750 armor reduces damage by 40% or 13,125 armor reduces damage by 60% at 86.
I believe it works like this but haven't tested at 86 cap yet.