No annual fee credit cards are the workhorse of most wallets: revolving credit lines that do not charge a yearly membership for the privilege of carrying them. Because the issuer is not collecting an annual fee, the card has to make money another way — typically through interest on carried balances, interchange paid by merchants, or paid optional add-ons. That is the entire economic model behind the category, and it explains why two cards with identical-looking rewards can behave very differently in practice.
The split that actually matters is rewards structure versus borrowing cost. On the rewards side, look at how points or cash back are earned, whether they expire, and whether categories cap or rotate. On the borrowing cost side, the headline number everyone quotes is the purchase rate, but the more useful figures are the cash-advance rate, the interest-free period on purchases, and the grace condition. A card with rich rewards and a short or conditional grace period can cost more than a flat-rate card the moment a balance is carried.
Comparing no annual fee cards is therefore less about hunting the biggest headline bonus and more about matching the rewards formula to your spending pattern, then checking the fine print on rates and timing so the card stays cheap when you do not pay in full.