Many people cross-train between Judo and BJJ. For them, there is no comparison. Rather, they take the best of the two sports and become a better martial artist. Judokas spend 70% of their time on takedowns, while BJJ concentrates on ground fighting, but if you want to become a good judoka, you need to have a good standing game and ground game.
Let’s take two people. Put one in Judo classes, the other one in BJJ. Both spend an equal amount of time training. The result will be that one would be good at the takedown, while the other one will be good on the ground. Though this is a little stereotypical since there is a lot of variation between coaches, clubs, and how training strategies/principles are taught, Judo encompasses both standing and ground game.
The reason why techniques are different is because of the rules. Sharing the same origin might make you think that both sports are the same. However, the rules make both sports quite different from each other.
You might have heard of Rolling BJJ, which is a kind of sparring. Rolling BJJ lets students practice and test skills and abilities in a controlled and safe environment. It is similar to any other sparring in martial arts, where the objective is to identify weaknesses to improve them. Instructors can easily identify opportunities for improvement, and this is one of the key objectives of rolling BJJ.
Students engage in grappling rounds with their teammates, similar to a BJJ environment. However, there is one major difference; the intensity is way less because the objective is to stay longer on the mat.
In Judo, you have 10 seconds to complete your submission. You can turtle up and stall. However, in BJJ, if you do that, the referee does not call matte and get you to stand up and start again. The match continues on the ground for the full-time duration. In Judo, you can go to guard until the referee asks you to stand up.
In Rolling BJJ, there are rules. When one attacks, the other one defends. If one is caught in a submission hold, he/she can tap then the match is won, which is the same in Judo. BJJ, there is an emphasis on controlling a position or practising specific situations. This enables an excellent learning opportunity for both combatants and also those who are observing them.
Instructors teach the student to approach teammates in a friendly and positive manner with the objective of learning. If one is caught in a submission, tap early and communicate with your teammate. It is also important that one may leave his/her ego outside the class and ensure that there is respect and honour. The objective is to learn from the mistake and not to take revenge
It is also important to understand that Rolling BJJ is influenced by the Brazilian culture while Judo is influenced by the Japanese culture.
Both Arm Bars in Judo and rolling BJJ are complementary to each other and allow both sports to learn from each other. It can be said that both sports are made for each other and perhaps the best thing that has happened to martial arts in general. Learning both of them at the same time could be advantageous. Especially for those who wish to compete.