Why sukha (third Jhana) is more refine than pīti (second Jhana)?
Lesser khandha = Stable mind state = Better happiness.

Vitakka, vicāra, pīti, and sukkha are acceleration of consciousness to access jhāna. the practitioner need them to develop jhāna-consciousness, until he turn to be professor in each jhāna. After that they become an obstruction of jhāna's stability.

Too many cooks spoil the broth.