ero2--Welcome to FlyerTalk. I have found it easier to redeem from AA than Delta, including getting 3 FF tickets to the Caribbean in Dec. for a peak week in Feb. over President's week. And MRTC is comfortable.
With that said, it is also correct that the miles pile up much easier on the Delta card. We use it exclusively for gas, groceries, Home Depot and the other always double miles, and try to pile on all of our spending during the double and triple mile promos. (Although I think nothing will ever beat that 50,000 mile match a couple of years ago.)
So, you are right that there are competing interests here. Get 'em both, so you have an AMEX and a visa, if you charge enough.
Djlawman