Simple question, I guess! Come with me:

Case 1:

CREATE TABLE example {
    id SERIAL PRIMARY KEY,
    stuff,
    stuff,
    details JSON
}

Case 2:

CREATE TABLE example {
    id SERIAL PRIMARY KEY,
    stuff,
    stuff
}

CREATE TABLE details_example {
    id SERIAL PRIMARY KEY,
    example_id INTEGER REFERENCES example(id),
    detailed_stuff,
    detailed_stuff
}

Which case would it be better, would have more perfomance?

I’m coding a quite big and important website