Fp Helm +6/25 DD
4x Chitin +8/15 health
You got more health and AC + the extra weapon defense, and other than spear defense you got somewhere between 1.66->2.5 times as much weapon defense. On average ppl will have twice as high damage on you than the chitin shield priest.
Oh Im sorry and what did you say? Priests can put on weapon defense armors and talias? GUESS WHAT!? So can chitin shield priests, and their bonuses are even more godly.