Leave AA for DL? You're on crack, right?
That stop in ZRH may be a little painful, but you'll get better service to ZRH and it's a relatively short flight to AMS. You'll also lose out on the ability to upgrade J to F on AA. Also, it will cost you plenty to upgrade those cheap coach fares on DL with segments. You will pay the same # of segments on AA
but you can also use miles to upgrAAde. DL restricts mileage upgrades to Y/B/M fares.