The content is accurate at the time of publication and is subject to change.
Cards offered by airlines sometimes offer features specific to the airline, which may be good for frequent travelers. However, they are limited in use, and especially if your air trips don't come down to Delta flights only, such card is more a pain, than a gain. Besides, those specific features are useless by and large, few people really know about them, let alone use regularly.
As a good alternative, you can apply for a miles rewards credit card offered by a major bank. There are travel credit cards that will allow you to earn more miles or points on all your purchases, which is not offered by the Delta card. Also travel rewards credit cards are cheaper as they do not have benefits you might not need. Travel rewards credit cards will allow you to earn miles everywhere and redeem earned miles with any airline of your choice, including with Delta.