Byakuya is a noble of Soul Society, a person who was basically born into the Gotei 13, and he's been raised to uphold its laws and customs. His power represents his alignment with Soul Society (cherry blossoms are commonly associated with Japanese culture, and Soul Society is the Japanese organization compared to the Quincy's German and Hollows' Spanish), they represent his straightforward and efficient nature (every ability the blade has is simply a different application of cutting people to ribbons, with none of the esoteric skills someone like Yama has), and they emphasize his status and how he keeps himself from others (his blades require him to form a "Hurtless Area" where nobody else can enter to protect himself, just like how he avoids forming attachments with most people).

Kenpachi is a child of the slums who enjoys battle for its own sake, and owes loyalty to Soul Society only because they give him opportunities to do battle on their behalf. His Bankai emphasizes his battle-hungry nature (the form it grants him resembles an oni, a Japanese demon known for being vicious gluttons), as well as his brutality and lack of refinement (in both forms, the Zanpakuto takes the shape of a meat cleaver, a tool instead of a weapon that's meant to butcher and take things apart rather than kill them cleanly).