The case for boring
Cards like the Citi Double Cash, Wells Fargo Active Cash, and Fidelity Rewards earn a flat 2% on everything: no categories to track, no caps to monitor, no annual fee.
For a surprising number of spending profiles, a single 2% card captures 85–90% of the rewards a carefully tuned multi-card setup would earn. If your spending is spread thinly across many categories — a little dining, a little gas, a lot of "everything else" — category bonuses have little to grab onto.
Where flat rate loses badly
Category cards pull ahead when your spending is concentrated:
- Heavy grocery spend: 6% (Blue Cash Preferred, capped) or uncapped 3–4x beats 2% by $120–$400/year at typical family grocery budgets
- Heavy dining: 3–4x dining cards out-earn 2% by 50–100% on that slice
- Rent: a flat 2% credit card usually can’t touch rent at all without fees; rent-earning cards exist specifically for this
- Travel booked through portals: 5–10x portal rates dwarf 2%, when the portal price is competitive
The pattern: each concentrated category is worth roughly (bonus rate − 2%) × annual category spend. One or two strong categories can fund an annual fee and then some.
The hybrid answer
Strong setups often look like: one or two category cards covering your biggest concentrated spend, plus a flat 2% card sweeping everything else. The hard part is choosing which category cards — caps, fees, and overlapping bonuses interact in ways that per-category comparison tables can’t capture.
That interaction problem is what the optimizer models: it routes the spending you enter across candidate combinations and reports when the highest modeled net value was proven within the selected catalog, constraints, and snapshot. Sometimes the modeled result is "just use a 2% card." That is more useful than a universal claim.