It’s a silly click-bait question, because even a single martial art is not a monolith.
Let’s take the example of BJJ. If it is presented as a game in which you learn to beat other BJJ players at BJJ, that is one approach. If it is, instead, presented as a self defense system against someone who has no concern for the rules of BJJ, that is a very different approach and the results will be different.
In the first scenario, the student will probably become quite competent at handling BJJ practitioners in the context of BJJ rules. If they choose to compete, they might do quite well. If some idiot in a bar decides to take a swing at them, they might do pretty well if they can manage to take things to the clinch, then the ground.
In the second scenario, the student will probably gain a wider understanding of martial arts and self defense outside of the context of BJJ. If they choose to compete, they might find they are fairly outclassed by students from other schools who have invested much more time in the specific tactics of the game of BJJ. If some idiot in a bar decides to take a swing at them, they might do pretty well if they can manage to take things to the clinch, then to the ground. They might also draw on any de-escalation or scenario work they have done in the broader context of self defense and try to avoid getting any deeper into the fight.
Is one better than the other for self defense? Maybe. It depends on what happens. The trouble with evaluating the value of martial arts when it comes to self defense is that self defense can encompass an extremely wide number of scenarios.
So what’s the answer? What is the best martial art for self defense? It’s very difficult to say. My inclination is to pick something that you enjoy, where the instructor is realistic about what they are focusing on, and where people train hard but with compassion.