The case for boring
Cards like the Citi Double Cash, Wells Fargo Active Cash, and Fidelity Rewards earn a flat 2% on nearly everything: no categories to track, no caps to monitor, no annual fee.
How much a single 2% card captures depends on your spending. On the site's own sample profile ($1,800 a month, led by dining and groceries), a flat 2% card earns $432 a year against $789.54 net for the best two-card setup the solver found, about 55% (that setup's figure is after annual fees net of the credits the catalog counts, and uses travel-point valuations at 80% transfer confidence). 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.
Updated October 2, 2026: an earlier version of this post said a single 2% card captures 85–90% of a tuned multi-card setup's rewards. We could not support that range, so it now cites the site's own sample profile instead.
Updated October 11, 2026: the sample profile's best two-card setup is now $789.54 net (it was $772.66), so a flat 2% card captures about 55% rather than 56%. The example now uses the same fees-after-counted-credits basis as the optimizer: the earlier figure subtracted each card's sticker annual fee, so it named a different pair than the optimizer returns for this profile. The pair is now Amex Gold with Capital One Venture X. Separately, the earlier setup counted the Bilt Obsidian's 2x on all travel, and Bilt's terms limit that rate to airlines, hotels, motels, resorts, cruise lines and car rental agencies.