A free rewards card is brainless. Just do it.
A fee based rewards card like the AMEX Delta card is awesome if you travel a lot and use a card a lot. I've got the Platinum card and I rack up 150K to 200K miles each year on it. Unfortunately, Delta along with most of the other carriers have changed their rewards program based on ticket expenditure and not so much for card expenditure. So you really have to weigh out the advantages/disadvantages on airline rewards.
Go with an American AAdvantage card. Way less miles for reward travel. Especially overseas. And you have the One World airline alliance to pick your flights from. I actually often prefer flying foreign carriers. Many of them treat you better and the food is often a lot better. Although, I'm not a big Airbus fan. So, I avoid them whenever possible. Don't like their seating.
