Actually wanna make thread about this because some ppl blindly choosing plate ._.
(Yes plate is quite the “best” in many case, but not every case)
And monster also has damage type (Slash, Pierce, Strike, Magic if it only cast magic), and if you wear the “weak” armor (example using Cloth vs Slash monster) you will also receive 50% damage
If you have High Eva / High DEX, You are better served with either Cloth or Plate because:
1 Leather Mastery Sucks
2 Archer Monster has the best acc, and their attack type are pierce, you cannot always miss their attack and once they hit you… BOOOM.
3 Plate will receive normal damage vs Pierce, has better mastery stat for monk (Stamina), you can evade most of Strike type monster because most of them has average or below average acc, and Slash monsters will only hit you for half of their damage.
4 Cloth will save you some mana potion, and… Save you from BOTH magic monster (15% reduction) AND Pierce monster (Pierce deal 75% damage to Cloth), you should only watch out of the slash type monster because they will deal more damage to you, but hey you have evasion 
On the other hand, if you are Full CON / High CON player, u actually better served with Cloth or Leather because:
1 Plate armor mastery sucks because you already have so much HP (except the stamina)
2 Most of Strike type Monster are heavy hitter with low acc, and you will receive more damage from them if you wear plate armor
3 Cloth from almost the same reason above
4 Leather will save you from Strike type monster, but its need some scenario to be effective, plus it give the most acc, something you might need if you have no DEX
(yes, leather sucks :P)
)