I have recently been pondering the same question, and came out on the side of miles. Which cards have you found that net 5% cashback? The only (U.S.) cards of which I am aware are either restricted to certain purchase categories or relatively low spending limits, or both. One could potentially get several different cards to maximize the number of categories earning 5%, but this would require a lot of coordination and work involving rotating quarterly categories -- ie, not simple at all —and I don’t think even then you could achieve 5% across the board.