Having the shield instead of the sword means other classes can get better attack bonuses with other weapons. The Spirit Shield is favored over the Spirit Sword as it's an off-hand piece of equipment that doesn't need to be actively used to reap the most benefits.
The Spirit Shield and Spirit Sword have similar stats but vary slightly. A Normal white shield or sword with 4 sockets is required to hold the runes. Players need 4 sockets in order to insert the runes Tal, Thul, Ort, and Amn to make the Spirit Runeword in Diablo 2: Resurrected.
