You may think the Amex Platinum and Business Platinum are too similar to justify having both, but I find their unique perks ...

This card's valuable benefits — including useful ones that other airline cards don’t offer — set it apart, making it worth the annual fee, even if you fly United only occasionally.

The card's rewards structure isn't the easiest to remember. But its useful bonus categories, flexible rewards and outstanding welcome offer make it a top contender among cash-back cards.