If you shared with us the specifics of your Delta spendings, it would be much easier for us to suggest something. Platinum and Gold versions of American Express and Delta Airlines co-branded cards are different in sign-up bonuses, rewards and annual fees. The Gold version has 50,000 miles sign-up bonus after $2,000 spent on purchases in the first three months. The Platinum version has 60,000 miles and 10,000 after the same amount spent on purchases. The Platinum version also has a free annual companion ticket and a Miles Boost feature, which gives you 10,000 bonus miles and 10,000 MQMs after $250,000 spent in a calendar year. However, these goodies come at a price of $195 annually.
What this means is that the Platinum card pays off if you spend over $25,000 a year or you are likely to get an economy coach ticket for a friend. It is far less likely to pay off if you fly once or two a year, then the annual fee makes it not worth it.
However, there are also cards that won’t make you choose anything. For example, the Discover it® Miles credit card lets you earn easily without any hassle and there is no annual fee at all.