I am not sure why people treat it like either/or, when in my opinion it's both.
Disarms seem to work better when the defender attacks the wielder, while simultaneously deflecting and controlling the weapon.
An unbalanced opponent is exponentially easier to manipulate, as any force he applies will serve to unbalance him further. This is true for very strong bad guys, possibly more so than for weaker ones.
Unbalancing is achieved through a combination of change in relative positions and centers of gravity, and through threats or strikes to areas that achieve a reaction - eyes, throat, floating ribs, groin, knees, ankles - whatever is easiest to treaten or strike in the instance.
Throwing a person who is set and balanced is hard. Throwing that same person in the direction to which they are already lunging (tracking a moving target) or flinching (avoiding or reacting to a strike) is much easier.