That would depend on the style of your game as well as the move. In AW, +Hard usually denotes your willingness to do harm, while +Sharp is more, like, focus, so stuff like shooting the zombie in front of you in the face might go that way, but lining up a shot at two hundred paces while the horde is slowly approaching you might use +Cool or +Sharp.

It's totally possible to set a specific stat for combat, though. Maybe +Hard for melee, +Sharp for ranged?