Fundamental or superficial difference?

[Spartacus Maximus]

Considering the most basic punching and kicking techniques of Okinawan karate(mah also apply other karate), are body mechanics significantly different? 

Is the striking point(big toe, ball of foot etc) the only difference between techniques? 

[camotheman]

Hmm, that’s a good question. I don’t think that is the only difference. In my opinion, the technique you’re executing has a few different aspects. If I’m going to strike with seiken, my technique will be overall completely different than let’s say, ippon ken. My power, wrist structure, target, and overall technique will be different. Even using koshi can be different depending on the variation of technique I’m using. Sure, in essence, it’s still a punch, but it definitely makes a difference in how I execute the technique. The same principle can be applied if I was kicking with the toe vs. the ball of my foot. 

This is a broad question with a very specific answer in my part, but I feel like that can be applied to any technique in karate. 

[Wastelander]

A lot of styles have adopted the same or similar mechanics over the past 100+ years, which likely come from Itosu Anko, as even some past masters who didn't train directly with him often learned his karate in school. That said, there ARE still styles with fundamental differences in mechanics. For example, KishimotoDi doesn't make use of hip rotation for power generation, but almost every modern karate style does. Motobu Udundi tends to "float" on the balls of the feet, but almost every modern karate style does not. Modern Shotokan and Kyokushin have made their motions so large that the mechanics can't help but be fundamentally different from the Okinawan styles they came from.

[Spartacus Maximus]

So how and where would the mechanics differ between a ball-of-foot front kick and one striking with the toes such as in tsumasaki or sokusen? How can it best be explained/decribed?

At first glance these kicks seem almost identical in movement except for the part of the foot used to strike with. There doesn’t seem to be a significant difference in the way the knee raised, extended and pulled back and set down. 
 

[camotheman]

12 minutes ago, Spartacus Maximus said:

So how and where would the mechanics differ between a ball-of-foot front kick and one striking with the toes such as in tsumasaki or sokusen? How can it best be explained/decribed?

At first glance these kicks seem almost identical in movement except for the part of the foot used to strike with. There doesn’t seem to be a significant difference in the way the knee raised, extended and pulled back and set down. 
 

I’m sorry, I misunderstood your question.

I would say that they’re pretty much the same in technique, speaking in terms of the knee motions, but they are different in execution. If I’m doing mae geri and striking with the ball of my foot, I’m driving my hip forward on the leg that I’m kicking with, to generate more force and power. If I was to do tsumasaki geri, I need to be much more aware of the structure of my technique, my hips will be more square than a regular front kick. If I lose that structure on a tsumasaki geri or use too much power, my toe / foot can bend to the left or right, essentially twisting my ankle to the side. 

Another thing is foot alignment, I’m flexing my toes up in mae geri to hit with the ball of my foot, whereas in tsumasaki geri I am tensing my toes to create that rigid structure. 

[aurik]

As I'm most familiar with Uechi-Ryu I'll contrast that with many of the other karate styles.  One major difference in Uechi-Ryu isn't just that we kick with the toes, it is also how the kick is executed.  We don't do a snap kick per se.  We aim to chamber the kick with the foot parallel to the floor, and then the foot penetrates straight forward into the opponent, aiming for vital targets such as the bladder or floating ribs.  In fact, one of the pieces of feedback I often hear on black belt tests is "kick forward not up".  

The second major difference, which our kobudo students need to often unlearn, is the way we use hip drive.  In shotokan or many other styles, when you perform a punch or other strike, you'll see your belt flying all over the place while your hips add significant power to your strike.  In Uechi-Ryu, the hip drive is still there, but much more subtle.  The hips only move a few inches and the belt just wobbles a little bit.