The answer to 'which is better underlayment or' is that underlayment is generally considered better than roofing felt or tar paper. Underlayment provides superior protection for your roof by creating a waterproof barrier between the roof deck and the roofing material. It helps prevent leaks, moisture damage, and deterioration of the roof deck.
Underlayment is a thin, synthetic material that is installed directly on the roof deck before the roofing shingles or tiles are applied. It comes in a variety of types, including asphalt-based, rubberized, or synthetic polymer-based. Underlayment is more durable, tear-resistant, and longer-lasting than traditional roofing felt or tar paper, which can break down over time and leave your roof vulnerable.