IMO the big 3 + AS are basically the same for the inflight experience for domestic travel. I have never noticed a huge difference between AA, UA, or AS and I seriously doubt that DL is any different. There are some minor differences that people on FT like to blow out of proportion but there's nothing significant.

The food may be slightly better or worse but are you really going to take a less convenient routing because of the food? They sell food at the airport that is far better than anything you are going to get on a domestic flight.