Plenor vs Vlemish
Vlemish provides a smaller mana bank but increased mana regen, and costs extra.
Plenor provides a larger mana bank but lower regen, and costs less.
Some characters are better off with mana regen for sustained battles and staying in the field.
A well played UB doesn't start expending mana until he's sticking around for the fight. So, a UB only needs to have a large mana pool: enough mana to use his skills as much as possible through the course of one battle. Vlemish doesn't provide enough regen to actually allow a UB to spit/grasp an extra time. So in the course of just one fight, Plenor is a better choice then Vlemish.
Simply, UB needs a large mana pool, not regen. Plenor provides that, and costs less.
