Hajime Murata is the archetype. His premise is a regular guy who gets to rub with magic users. He has no magical abilities of his own, so in order to be level with them he is awarded a special ability: smooth-talking his associates. As a result, they are sufficiently enthralled to let him into their inner circle, and so the adventures and whacky hijinks ensue. So, this is the basic formula. It allows to avoid the trope of the guy who suddenly pilots the mecha/ship/etc. without any training. For some reason the populus believes that it's natural for such smooth-talking to be innate and accomplished without any training under the difficult conditions of extemporaneous communication; all the hero needs to do is be the nice himself and presto! everyone is charmed.

Toru Honda is essentially a girl Hajime, and so in addition to the power to smooth-talk she commands the power of girls. She gets to demonstrate her enormous skills at running the household and adhering to gender roles. She would be impressive even if she said as little as Kasumi Tendo. This obscures her smooth-talking talent, but it's still quite present. When applying it, Toru often is a one-trick pony, trying the same approach of "let's all get along" and big-eye charm even to utter assholes who by all rights should not be vulnerable. But it's not quite as dire and she can be smarter than that if she wants to [citation needed -- rewatch how she dealt with the little rabbit jerkface; other later relations?]. Maybe she's just intellectually lazy (and lacks good sleep due to all the chores).

Ryuushi Shiratori is different in the way that he has to excercise his smooth-talking talents on manifestations of Kozue. That is the secret circle which accepts him, and the obvious circle of residents is slaved to it. They don't even have any extraordinarily abilities; they are but keepers of the secret. The only exception to this is Tamami, and perhaps this is why Shiratori has to deal her and her alone such a crushing defeat with his golden tongue. The raw difficulty of the tasks in front of Hajime and Shiratori is about the same, that is to say, they are very hard. However, Hajime's responsibility is greater, he cannot fall back on his drawing skills for support, and he does not permit others to mop the floor with him as much. This is why he is the archetype.

Taro Hanaukyo is different from everyone else on this list by virtue of possessing a proper authority. So, strictly speaking, he doesn't have to be on top of the smooth-talking game. We saw plenty of effective leaders who weren't as astute in this regard. However, he is good at it, which helps. As it was argued elsewhere, it's likely that Taro is at least partially telepatic. Still, even if he relies on the additional information obtained telepatically, he has to talk overtly to his subordinates to win their trust and make them work smoothly as a unit, so he certainly belongs into the group anchored by Hajime.