One-day TripAdvisor: 25x miles beats 30% gift-card credit.
Capital One's deal of the day on TripAdvisor pays 30% back via the public Capital One Shopping portal or 25x miles through Capital One Offers for cardholders. The 30% back is gift-card credit, not cash; the 25x miles earn transferable Capital One miles. Past targeted email offers have gone as high as 70% back, but the posted rate here is 30%. At these rates, the miles are the better play unless you value gift-card credit over transferable miles. TripAdvisor bookings may initially track as ineligible and only credit after travel completes.
the play
Use Capital One Offers for 25x miles on any TripAdvisor booking you already planned before 11:59pm Pacific on 8/24, and expect the credit to post after travel completes.