I use Discover wherever it's accepted because I get cash back bonuses. In a pinch, I use a GM MasterCard, for the points towards a new GM car. Don't need those now, 'cause I don't plan on a GM vehicle being my next car purchase. So I'll use my AT&T MasterCard, so they won't close the account due to non-activity. I was warned!
I'm a "charter member" of Discover, which means I pay no annual fee. Nor do I pay an annual fee for either MasterCard. The AT&T card doubles as a phone card, which I used years ago on business trips. I guess that's so retro now.