Guard of Valor instead of Naliah's Robes?

[OUTLAWS The Machine]

I'm not seeing why everyone says get Naliah's instead of GoV for casters.

Guard of Valor
Hits +40
Intelligence +15
Bonus to Intelligence cap: 5
Dexterity +15
Strength +15
Bonus to Dexterity cap: 5
Bonus to Strength cap: 5
shield debuff
Bonus to spell range: 4%
Bonus to magic damage: 4%
dmg-over-time proc


Nailah's Robes
Intelligence (or Piety) +15
Crush 5%
Slash 6%
Thrust 6%
Realm Lore
Bonus to spell range 4%
Bonus to magic damage 4%
dmg-over-time proc