Is brazilian jiu jitsu good for self defense?

Brazilian Jiujitsu, or BJJ, is known as the gentle art in martial arts.  BJJ can be practiced in two modalities: Sport BJJ and the other as self defense. Sport BJJ is competitive and based on a point system based on a competitor being awarded a number of points based on advancing to a more advantageous position. Alternatively, a competitor may immediately win the match by submission. When BJJ is used in self defense, the goal is usually to subdue an attacker.  Since BJJ is mostly grappling from the ground, it can be a highly effective practice for self defense as many street fights end up on the ground. While many of the techniques are intended to immobilize an opponent, it can be less effective if the opponent has an unfair advantage such as the use of a weapon. Practicing BJJ routinely will prepare the practitioner mentally for physical combat which can be advantageous in a self defense scenario. Another reason BJJ can be viewed as good for self defense is that there are techniques that can work well for different body types that level the playing field for even smaller or weaker opponents. If both opponents are trained in BJJ, size and strength can become a larger factor.  Routine training can also lead to increased physical fitness as classes can be quite rigorous and physically demanding. Some may argue that more ruthless martial arts are intentionally designed for self defense and therefore may be more effective.