I feel like there's two factors being discussed here. He does break them down in the video, but it does make it difficult to compare the two when you're changing multiple things. The factors are the motion of the kick and the striking implement.
Motion of the Kick
In my Taekwondo school, we only really go over the traditional style of the side kick. With that said, it doesn't really feature heavily in my Master's style. I think it's more used in forms, and as a stepping stone for teaching the back kick (which later on we teach details that take it away from being a turning side kick) and the hook kick. It's also used in the double back kick. World Taekwondo heavily favors roundhouse kicks, head kicks, and turning kicks; so we don't really go in-depth on front kick or side kick.
In my curriculum I'm developing, I do want to go more in-depth. I still have the traditional style of kick as my basic side kick. This is for a few reasons:
- Differentiate it enough from the front kick and get students used to pivoting
- Prepare students for other kicks (notably back kick and hook kick)
- It's closer to the style of kicks used in the poomsae
In green belt, I plan to work on the thrusting front kick with the ball of the foot, instead of the rising front kick with the instep. At red belt, I plan to expand it further and introduce the concept of what I call "whip kicks", which is taking the traditional form of the kick and replacing it with a faster version. Most of these are for WT sparring, such as:
- Whip Crescent Kick - chamber instead of swinging the leg through the full arc
- Whip Back Kick - Starts by flicking your foot toward the target instead of pivot and chamber
- Whip Hook Kick - A fairly linear hook kick, as opposed to the traditional wheel kick
- Whip Side Kick - A side kick that starts off as a front kick
I agree 100% that this kick is easier to hit with than the traditional side kick, for both reasons that are stated. It's faster, and it uses a generic chamber that can be for a number of kicks. I feel that a higher belt should be able to learn a variety of ways to do the kick, and don't want to confuse them early on.
Ball of the Foot
I'm going to disagree with everything he said about the ball of the foot, except for the increased range.
The ball of the foot is actually a pretty large area by itself. You're also probably going to get some of your toes in there as well. I would say that of the three (blade, heel, ball), the ball of the foot probably has the most surface area in most cases. On a heel kick, even if your entire foot hits, the heel is still the tip of the spear.
Then there's the question of stability. As you get further away from the ankle, the foot is much less stable. That instability can cushion the blow. The heel and the blade of the foot are going to be much more rigid than striking with the ball of the foot.
I do feel there's a risk of injury of the toes when using the ball of the foot. I suspect this is why some Karate styles do the front kick with the heel. It's why I will not teach the ball of the foot for the roundhouse kick.
The argument for extended range on the kick I agree with. At this point it's basically a front snap kick with your hip rotating into it. However, I think you're sacrificing solidity for reach.