Kind of! The Soulbastion has best stats for defense, its extremely good for tanking and it also has an extra death defense. But, the Eldritch Shield (even if it has less defense in gral) has the plus of the damage reflection, this is good for aumenting the damage of the ek, thus rising the xp/hr. In fact an ek can reach its maximum of xp/hr solo by wearing this shield (or at least before sphinx were nerfed lmao).
So both of them are BiS shields, but since less people has access to The Brainstealer and its a very rare non guaranteed item, the Eldritch Shield is more expensive. In comparison, the soul items are guaranteed for people finishing the quest, and they're also possibly looted by people doing the bosses or hunting in Soulwar.
You see a soulbastion (Def:42, protection physical +10%, death +10%).
Imbuements: (Empty Slot).
It can only be wielded properly by knights of level 400 or higher.
It weighs 58.00 oz.
You see an eldritch shield (Def:39, 42 Damage Reflection, protection physical 4%).
Imbuements: (Empty Slot).
It can only be wielded properly by knights of level 270 or higher.
It weighs 66.00 oz.