Just as important as the capacity and brand of your Pepper Spray, is the spray pattern. There are generally two types of spray patterns: a stream pattern which gives good range but requires aiming directly at the face; and a cone mist, also known as a fogger, which has a shorter range but does not require true aiming.
In addition to these factors, there are two other important comparisons. First, if there is a breeze, the stream spray is more controllable. The cone mist can be blown off target or even back at the sprayer. Second is the question of inhale ability. OC works best when it hits the eyes and when inhaled. The cone mist is inhaled instantly while the stream may require longer exposure to cause coughing spasms. With all types of sprays, it is critical to hit the attacker in the face!