In the wizarding world, mundane armor is useless against spells. The best way to survive a duel is to avoid being hit.

Cloak Cost Armor Class (AC) Stealth Weight
Cloak - Winter 9 g 11 + Dex modifier (max 2) Disadvantage 20 lb.
Cloak - Silk 25 g 11 + Dex modifier 12 lb.
Cloak - Shield 75 g 12 + Dex modifier 12 lb.
Cloak - Demiguise 400 g 13 + Dex modifier (max 2) Advantage 18 lb.
Cloak - Disillusionment 750 g 14 + Dex Modifier Advantage 10 lb.