This question seems to be asked frequently, and each answer is usually based on opinion. After much thought, AL is better than HP. That is to say that using insignias that increase armor are better than using survivor's insignias. That of course is not to say that extra HP is useless.
Example: Level 20 Assassin - Frontline
Full Nightstalker's Insignias
+1 rune of choice
Highest Vigor
3 Vitae
You still get the HP, but with added armor. Here is why AL is better than HP. AL reduces damage taken in the same way that having high HP takes an enemy a longer period of time to kill you. But, when having low HP, when you get healed, you still heal for the same amount. With the above listed runes and insignias, without factoring in weapons, you would have 85AL while attacking, and a maximum of 560HP (if using a superior vigor) as opposed to the extra 40 you would get for full survivor (which isn't much). If you get hit for say 100 damage with 70AL and 600HP, you would take 84 damage after damage calculation, bringing you down to 516. If you take the same amount of damage with 85AL and 560HP, you would take 64 damage after damage calculation, bringing you down to 496, lower than that of the other. But if each were to take that same amount of damage multiple times...
600 - 84 = 516 | 560 - 64 = 496
516 - 84 = 432 | 496 - 64 = 432 (After 2 attacks, they are both left with the same amount of health)
432 - 84 = 348 | 432 - 64 = 368
348 - 84 = 264 | 368 - 64 = 304
264 - 84 = 180 | 304 - 64 = 240
180 - 84 = 096 | 240 - 64 = 176
096 - 84 = 012 | 176 - 64 = 112
012 - 84 = 000 | 112 - 64 = 048
It may only be by 1 attack, but the one with survivor's insignias would die first without healing. But even in the event that they were both healed for say 150HP, the survivor's insignias sin would be healed for 25%, while the nightstalker's insignias sin would be healed for 27%. Not much difference, but it seems that the sin with a higher AL would both survive longer and heal for more. Now this is only one case, and the data given may be somewhat biased from other situations, but generally speaking the case is usually the same.
Now I've shown my thoughts, what are some of your thoughts?
PS: I still usually use Survivor's Insignias simply because they are available to all professions and can be used globally across all characters, heroes, etc.
Damage calculation data: http://wiki.guildwars.com/wiki/Damage_calculation
J


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