Chase Freedom Flex vs Freedom Unlimited
What each does
The Freedom Flex earns 5x on rotating categories that change each quarter (on up to a spending cap, with activation), plus a standing 3x on dining and drugstores. The Freedom Unlimited earns a flat 1.5x on everything with no categories to track. Both have no annual fee and earn Chase Ultimate Rewards.
They are better together
These two are designed to complement each other: the Flex covers rotating bonus categories and dining, the Unlimited covers everything else at 1.5x, so between them nearly every purchase earns a bonus. Held alongside a Sapphire, their points become transferable. This is the heart of the Chase trifecta.
If you must pick one
If you will activate the quarterly categories and want maximum category earning, the Flex earns more. If you want a simple, no-effort flat rate on all spending, the Unlimited is easier. But since both are free, most people hold both. Pair either with a Sapphire to unlock transfers.