Volcarona would be my pick
True, Durant has better Physical capabilties and Volcarona is Special
Durant's stats are; 58/109/112/48/48/109
Durant is the fastest of all Steel types, and has a good defensive typing (Bug/Steel). Durant, if boosted by Hustle also becomes one of the most deadly sweepers, especially with Hone Claws. Unfortunately, it's horrible HP and special bulk allow it to be easily taken down
Volcarona's stats are 85/60/65/135/105/100
Volcarona is one of the largest threats in the game. With an awesome boosting move in Quiver dance & reliable healing in the form of Roost /Morning sun, as well as awesome offensive STABs with Bug & Fire. It is however, extremely weak to Physical attacks and stealth rocks.
Anyway in the end, I would choose Volcarona. If you invest a little bulk, it can still take Priority attacks like a boss, since it resists the majority of them. Special attacks are a pushover for Volcarona, especially with some quiver dances under it's belt. Due to it's ability to set up, better coverage and reliable healing, it beats Durant in most cases.
