This in context with the original question however, made me wonder. Is this usual style for the US/ New York City: that a kid (I can’t see how old the son is) goes to a three-month (!) karate class and neither the pupil nor the father is explained by the instructor on what karate is for and not for? That is, Karate is a competion sport primarly (today), not a self-defense; it takes years to become good in it; and besides the physical component there’s the philosphical concept e.g. meditating before and after class?
Is this done in the US commonly, that - to cite what I saw from Hollywood - the Kobra Kai style of teaching Karate (from the Karate Kid movies - the “bad guys”) is more common (normal?) than the Mr. Miyagi technique?.
I would switch away from any school that doesn’t include the philosophical aspects, or doesn’t explain how long proper training is going to take before the three month course starts.
I would switch away from Karate generally if self-defense is the main interest of the boy, and put him into a good jiu-jitsu class or Aikido class. (Or Capoeira/ Krav Magda, but personally, I prefer the philosophical aspects of Budo.) And I would make sure I had a good instructor, not a badass who blusters about three months being worth anything more than the most basics basic.
As for the question above, if we use primarly self-defense martial arts instead of primarly competion martial arts (where everybody uses the same technique, unlike a weightlfter in the street), I would put my money on the Aikido/ Jiu-Jitsu black belt any time. Not only because a weight lifter has a lot of mass, but no trained speed for an attack, or the stamina to last - street fights are a matter of minutes, because the aim is to disable the attacker long enough to run away, or put him into a safe hold - but because of simple physics.
Jiu-Jitsu (which BTW is the offical self-defense taught to the Bavarian police, so it obviously works to some degree) and Aikido (which was specially developed for elderly kids and women with weak muscle mass) both work on the principle of deflecting a blow instead of parrying, which takes far less strenght, and then (esp. in Aikido, everything moves in circles) turning the attack back onto the attacker (see the philosophical element). So if the attacker is 100 pounds heavier than you, the skinny defendant, physics work to your advantage, as it’s easier to turn him around and onto the ground.
Likewise, a lot of levers used to immobilize somebody work on anatomic principles that apply to every human, even to the Hulk. If I put your straight arm into a lever where your elbow is the pivot, then I need very little strenght to cause you a lot of pain, and your 200 pounds won’t help you anything. (True, the individual pain point can very - we tried in class the classical police-hold of arm behind your back, and with some people, I had to move the arm high up before they noticed anything. But it did work in the end, invariably.)
Lastly, the advantage of Jiu-Jitsu and Judo over Karate - and considering the point about Muscle memory made in the first post - is that you learn falling techniques which are useful even if you’re never attacked in your life. For example, an instinctive reaction to falling forward is to catch yourself on your hand. This will break your wrist bone, because the weight is too much. You can overcome this reflex with training however, and slam down your full underarm, keeping your body under tension. This will distribute your weight enough that you won’t break your bones. (Interestingly enough, I was taught a similar technique for proper rollerblading, how to fall using your protectors, first onto knee pads, then elbow pads, and only at the end the wrist pads.)
