The entire Akatsuki has this big brother little brother dynamic in their two man cells. It just so happens Sasori has a dude on the caliber of Deidara submissive to him.
Itachi, Sasori, and Kakuzu by default have the portrayal edge over any of the little bro counterparts in the Akatsuki which are Kisame, Deidara, Hidan respectively.
And the thing is the two man cells are fully expected to be unstoppable even up against bijuus. So the "leaders" of those cells get bonus points for leading the way. And they were grouped separate from each other imo.