In a date-driven release, the most critical aspect is to ensure that the release date is met, even if that means compromising on certain aspects of the product. A feature buffer allows for this flexibility by prioritizing essential features while designating less critical features as optional. This way, if unexpected issues arise, these optional features can be deferred or excluded without impacting the release date. Therefore, for a date-driven release, a feature buffer is most important to accommodate uncertainty and ensure the deadline is met.