It'll most likely simply have slightly higher defensive stats just like with any other +1 gear.
You never know.
Keep in mind that back in Final Fantasy XI, +1 versions of all the different novelty and event attires had quirky little effects and functions that you could take advantage of. If I recall, one of the +1 swimsuits allowed you to teleport to Purgonorgo Isle once every 5 days or so, the +1 Dream stuff gave you a status buff for eating milk and cookies, and so on and so forth.
So it isn't outside the realm of possibility that the +1 version of event gear in FFXIV goes the same direction.
____________________________Final Fantasy XI Character(s) Name:
Carbuncle (RIP Gilgamesh) Jobs:
99DRG, 99PLD, 99RDM, 99WHM | Everything else: 50-60 ~Retired.~ Final Fantasy XIV Character(s) Name:
Satisiun Desain Server(s):
Sargantas (primary) DoW/DoM/DoH/DoL: