Masterly said:
Well the thing about Sasuke is that his charisma comes solely from his looks and intensity. As far as social interactions go, he's got the charisma of a hammer.
Not even a particularly well crafted hammer.
It's always been my policy to arrange stats (assuming d20 stat scaling) into three distinct categories. If 18 is the highest you can achieve naturally, then you break up the 18 into three general spheres. 6 is very good, and 1 is all but a lack of the trait.
Social Interaction
Magnetism
Appearance
Sasuke ranks very high in the latter two but when it comes to his ability to interact with his peers, his development and growth was all but retarded by his brother's actions. 1-4-6 would make a very attractive character who naturally draws attention his way but comes off as needlessly cold or even distant in conversations.
Naruto on the other hand would be something like 4-6-3. He comes off as boisterous and annoying but that kind of energy is strangely infectious if you spend enough time around him for it to infect you. And believe me, you will be infected.
It's not perfect but I figured I would at least try to explain away my decisions for their respective charisma.
I think you're underestimating Sasuke a bit and overestimating Naruto in charisma.
I presume that we are talking Pre-TS Naruto here since that is when this story takes place. He is short, rude, crude, and desperate for attention to the point where he does things that garner negative attention. He's socially inept, calling people names even when he does not know them well (Fuzzy Brows, etc). He is not someone seen as a leader and IIRC Shikamaru even makes a crack about how Naruto is the type who would never be a storybook hero (I think during Forest of Death). He's not physically attractive -- at least not yet, not as a 12-13 year old.
The bottom line is, other than his Ninja Jesus moments Naruto is terribly lacking in charisma. Those Jesus moments come from his ability to "see through the darkness" and connect with the dark feelings someone has. Then literally beat those feelings out of said person.
I'd give him:
Social: 1-2 (rude and disrespectful, does not follow social graces at all)
Magnetism: 3-4
Appearance: 1-2 (at this age -- it's implied he is much more attractive Post-TS)
Total: 5-8
Post-TS would be more like:
Social: 2-3
Magnetism: 4-5 (again, not counting Ninja Jesus mode)
Appearance: 3-4
Total: 9-12
Sasuke on the other hand might be rude and hard to cooperate with towards his peers, but his "too cool for school" attitude is at least partially fanon in origin. For example, if you go back to chapter 538, you'll see that every rude action Sasuke takes is actually a response to Naruto, who is acting like a complete and total jackass. In appearance there's no question of Sasuke's rating, and when it comes to magnetism, everyone tends to be drawn towards him and focus on him.
Social: 2-3 (lacking in teamwork and respect, but at least understands social graces)
Magnetism: 4-6
Appearance: 6
Total: 12-15