Do you do a lot of travel? Between DL and AA the difference is which carrier you expect to fly. If you're at one of those hubs (i.e. CLT or ATL) you'll find the nonstops convenient. They come with free checked bags and priority boarding which pays for the annual fee. I think AA miles are 'worth more' than DL but it depends on route and in general air miles aren't super valuable so between the two I'd do neither unless you need the bags.

I'd add in the Amex Everyday credit card as an option too. It's no annual fee and earns 2 points on groceries and gas, and a bonus 20% points if you use it 20x a month. Like Chase, the Amex points are more flexible than just airlines, although redeeming for airlines is often the best use at least there are more options instead of just one program.

If you have Costco near you, their credit card (a Visa card) has excellent perks and tiered bonuses (4% fuel cash back everywhere, 3% on restaurants and travel, 2% at Costco, 1% elsewhere) redeemable as an annual certificate but requires a Costco membership ($60/yr).