Vitality or toughness

Vit vs Toughness is heavily debated but here is the math reality for those who want hard numbers over opinions.

First off, different armor classes get different amounts of armor by adding toughness.
Heavy armor classes get +36% armor by adding 798 toughness
Medium armor classes +39% armor by adding 798 toughness
Cloth classes +42% armor by adding 798 toughness

Result: low-armor classes get larger armor bonuses by stacking toughness than heavy armor users.


Second, different professions get VERY different amounts of health by slotting vitality.
Warrior and Necro get +39% health by adding 798 vitality
Mesmer, Engineer and Ranger get +47% health by adding 798 vitality
Ele, Guardian and Thief get +64% health by adding 798 vitality

Result: Ele, Guardian and Thief get huge benefits from Vitality whereas Necro and Warrior get almost half the benefit.
Mesmer, Engineer and Ranger are in between.



This is why there is little point in slotting full defense and sacrifice health on say, a Guardian that would get huge health amounts from vitality (which would end up largerly outperforming toughness stacking).
Slotting your Guardian with +798 VIT means he can take +64% damage than normal.
Slotting your Guardian with +798 TOU means he can take +36% damage than normal.

http://www.guildwars2guru.com/topic/39575-toughness-or-vitality/page__st__30