Try using a laser rifle against someone wearing metal armor, then try again with plasma. You'll know the difference. This also answers your question regarding leather armor and metal armor.
The Plasma Rifle could be a nice weapon, but his range is much too low.All weapons used in pvp have a better range (Avenger, M60, Rocket, Sniper, Gauss, Gatling and Laser Rifle), so if we could compare it directly you should take 2 bursts in your face before making one of your über-powerful-plasma rifle critical.Though I think this weapon is good versus mobs or for killing some random bluesuits.
,but what makes the plasma rifle do better crits...I don't see anything on the weapon itself that would indicate it does.I've gotten 200 crits from both of them
it does better crits at head shots, always.
Reasoning 101.Plasma is massively underperforming ATM, only being better than laser rifle in plasma type of damage. Nonetheless in terms of bypasses, it is neglectable.