Guild Wars 2

I have just made some nice armour and it has some vitality on it. This is fine as it is what I wanted. However I now have to pick a Rune.

So should I go for. Rune of Necromancer or Rune of Undead?
The difference is basically, vit or toughness.

I have about equal vit and thoughness currently, so which should I pick?

Toughness

You already cleanse enough with basic water traits and those are the main reason to do Vit.

And I vote for Undead