| VarisianViscount |
Both spirits have manifestations that lend themselves to immortality, albeit in different ways:
1) Life requires contingency via Speaker for the Past archetype or Lore spirit's Arcane Enlightenment hex, or miracle via Serendipity Shaman archetype; Heavens auto-reincarnates if dead for 3 days.
2) Life is immune to death effects, meaning breath of life and reincarnate contingency/contingent spell will always trigger; Heavens gets Wisdom to Fort and Ref and thus reduces the chance of succumbing to a death effect (which ideally would be the minimum 5% chance of rolling a natural 1, possibly even smaller with re-rolls).
3) Life can't die from 0 points in an ability score (i.e. the Con score), since they can't be reduced below 1 (which also means less chances of becoming helpless and then being coup de grâce-d); Heavens has nothing of the sort.
Between the two, I feel they are equal in potential, since the only time death by ability drain matters is if it turns you into an undead before reincarnate can trigger, but it is still a weakness of the Heavens spirit nonetheless. On the other hand, Heavens offers more universally useful abilities, spells, and hexes in my opinion, while Life shoe-horns you into a healer role.