• I would rather ('I prefer', 'I would prefer') is used as a modal auxiliary verb. It is followed by the infinitive (without 'to') when its subject is the same as the subject of the next verb. This happens when we talk about what we would prefer to do.
I would rather (or I'd rather) stay with you. I would prefer to stay with you.
What would you rather do instead? What would you prefer to do instead?
She'd rather not see me. She'd be happier not to see me.
Wouldn't you rather stay on the beach? Wouldn't you like it better if we stayed on the beach?
• Would rather is followed by a past subjunctive when its subject is different than the subject of the following verb. This happens when we talk about what we want someone else to do. (The past subjunctive is conjugated in the same way as the simple past, except for 'to be'.)
I'd rather (that) you came another time. I'd prefer you to come another time.
She would rather (that) he weren't so angry. She would prefer him to be less angry.
Bruno would rather (that) Icarus didn't stay so late at the office. Bruno would be happier if Icarus didn't stay so late at the office.
Note: The verb to prefer is a synonym of would rather, but has a slightly more formal, impersonal tone.