Complete the introvert's honest reply to a Friday night party invitation.

To be completely honest, I ___ stay home and watch documentaries about cheese than go to a crowded nightclub.

The correct answer is would rather.

"Would rather" is used to express a personal preference or choice between two things. "Had better" is used for strong advice or warnings about negative consequences, which doesn't fit this context. "Would better" and "had rather" are incorrect mixed forms.