|It protects its wearer from the effects of both cold and heat.|
A shield of resistance is an amazing find, far more useful than any other possible shield ego unless you already have full resistances from other sources. Should you find a shield of resistance of a size easily usable by your species, strongly consider investing in using a shield if you're not already doing so.
A robe of resistance is also extremely useful, allowing many species with equipment restrictions to fill out their resistances easily. However, the low AC and complete lack of GDR on robes may make heavier armour preferable, especially if you find a randart with a better assortment of resistances. Even so, a robe of resistance is still an excellent choice for casters and EV-based fighters.
A scarf of resistance is a good compromise for getting more resistance without entirely sacrificing AC. You'll miss out on the 3 extra AC from having an enchanted cloak, but having the extra resistances will often make up for that and it's nowhere near as impactful as choosing to wear a robe over heavier armour. Depending on your other equipment, you may find a cloak of invisibility or magic resistance (or even an artefact with a good array of attributes) more useful, especially if you already have decent amounts of fire and cold resistance.