Depends on your build. Lava armor is more for applying debuffs or a little extra damage. Guardian armor is more for extra defense and survivability
True, it depends. I find Lava armor more useful on my build than Guardian. Keeps me alive
After using both for a while.
I think Lava Armor is better as after equip with mana reserve you can just keep using the skill and the Damage is higher compare to Guardian.