The element you're talking about is in the Magnificent Samurai, only it is diluted and they did switched characters. Many people get slightly bewildered by the Magnificent 7 because the character translations aren't straight translations.
For instance, the drunkard who claimed he was a samurai in the Seven Samurai is combined with the young kid in the Magnificent 7.
But if you also notice, the Kid in the Magnificent 7 is the one who lays down his arms as a gunslinger. Unlike in the Seven Samurai when the kid just decides to stay but keeps his sword, in the Magnificent 7 it's made very clear that he will never pick up a gun again, and that he was and always will be a Farmer.
You are right though, there are no Top Knots, but that's a socially limited statement to Japan. I have to watch my Magnificent 7 dvd again, but I think that the Kid actually takes off his Gunbelt and lays it down when he goes back to the woman (note she does not chase after him). Remember, in most Westerns, when a gunslinger takes their gun off in that fashion (at the end of the movie, with no real reason to take it off), it means they are retired.
Anyway, Both movies have things that the other movies lacked. Magnificent 7 does have more explanation of why the bad guys are bad. Seven Samurai have more of the Samurai Code of Honor and the dying Feudal era.
I love them both, Akira loved them both, and think that if anyone watches one, they should watch the other ^_^
Ditto for Yojimbo and Last Man Standing (both were written by Akira).