Dramatic uniforms, moments of glory, but basically cameo appearances in the real drama of the battles.
Still, if we want to put put the building blocks of a Prussian infantry division, we have to represent the cavalry regiment - 5 to 6 hundred sabers.
As a side note it is truly amazing how many books go onto loving detail about the headcount of a French or Prussian infantry company, but breeze past a cavalry squadron as if everyone knows what that is.
Cavalry divisions seem more variable - 2 brigades generally, plus a battery or two of horse artillery. Sometime three regiments to the Brigade, sometimes two. Sometimes even three brigades. Often of different "types" within the same brigade.
Anyway, I am inclined to represent cavalry regiments as regiments.