There's a lot of disinformation about martial arts in any online discussion, especially because people are obsessed with determining which martial arts is "the best". That's a sort of reductionist argument that never takes into context the history of each martial art and why/where it is effective or ineffective.

Let's start with some history: Judo was never heavily practiced historically, because you had a sword. Judo techniques were used as a last resort in case you lost your weapon. In a society where the peacekeepers carry weapons, you are at a serious disadvantage with any kind of unarmed combat, be it BJJ (which I practice, for sport), Muay Thai (which I practiced briefly and is effective in 1:1 situations in a stand-up and clinch), even Krav Maga (I tried this), or Chinese martial arts.

So here's an argument for why certain martial arts are "better" than others, depending on the situation and the era you live in:

Kendo/sword martial arts - you are likely going to war. The Chinese martial arts fall under this category, where you can quickly use certain forms to train thousands of troops at once to be "more ready" in general warfare than your enemy. Your troops will have slightly more conditioning, and practicing forms lets you have a 1:many trainer to student ratio. Even if the martial arts are not the best for close quarter 1:1 combat, or ground fighting, it makes no sense to spend time training your troops for these situations if the odds are VERY stacked against them in a wartime situation.

Krav Maga is a great martial art to teach for modern, urban self defense because the movements are basic. If you might end up in a bar fight, for instance, Krav Maga teaches something called stacking, where your goal when you have to maximize your chances of getting away from multiple attackers is to quickly subdue one attacker, then using head control, using that attacker's body to defend your own while you create space so you can escape. There are more advanced techniques that teach knife or gun defense if you are caught off guard, but it should be noted that you are probably at a disadvantage unless you are highly skilled if someone with a weapon attacks you! Training Krav Maga takes a bad probability of survival and turns it into a less bad probability.

Back to Judo: judo and karate took off as effective when peacekeepers could not carry weapons, and had to learn to effectively do their jobs without weapons. The key here is that society had to chance so that weapons were only carried by the warrior caste.

Filipino martial arts - unarmed, sticks, knives. No swords or spears, because this isn't what they went to war with. Surprisingly effective now, because you are likely to have a cane or umbrella, and you will have a slightly better chance defending yourself against a knife attack, which a modern attacker is more likely to have than a sword or a spear.

Now where does Brazilian Jiu Jitsu, which many people talk about, fit in? Brazilian Jiu Jitsu is an extremely effective martial art for one-on-one, unarmed confrontations. For children, if a bully throws you to the ground and gets on top of you and starts to hit you, you can escape and get away. If ONE PERSON attacks you in public without a weapon and you both go to the ground, you can probably subdue or escape if you have practiced BJJ. If two people attack you, or if it's one group on another group, BJJ is probably not so effective. I saw a version of MMA on TV that was effectively a 5v5 team fight, and it quickly turned into who could tap or KO a another member first, then it became a 5v4, and 5v3, and so on. The effectiveness of BJJ in group fights is greatly diminished - now we are back to martial arts like Krav Maga where you might have learned to group fight or even the Chinese martial arts.

BJJ and Muay Thai have really taken off because of MMA/UFC. The rules used to heavily favor BJJ practitioners, who in that particular environment, thrive. Karate practitioners were not traditionally used to ground fighting, and the Jiu Jitsu fighters would stick to their strategy of taking someone to the ground and quickly submitting them. UFC is a 1:1, no-hitting-eyes-or-neck-or-groin fight. No stomping. In the early era of UFC, there weren't any rounds. This GREATLY favors BJJ practitioners, who can simply hold someone indefinitely on the ground and tire them out. If you've never grappled before, even if you are in great shape - HOLY MOLY prepare to get wiped out in minutes.

Many of you may disagree with some of the details of my interpretations, but the general spirit of my argument is this: different martial arts thrive in different eras because society changes. Claiming one martial art is better than another without adding context is disingenuous.