SEA is my base. I had a terrible experience with an AS supervisor at SEA last year. They broke our bag between SJD and LAX last year; though I escalated at LAX, they directed us to escalate at SEA. The supervisor at SEA accused me and my wife of breaking it and displayed condescending behavior. She flat out lied to us that AS did not fix bags and that it was on us to get it done and she would just give us some miles or something like that. I had to escalate to her supervisor and one step further who apologized and confirmed that they did, indeed, direct-repair bags with their service provider.
Delta? I stupidly misread my flight itinerary one time at SEA and I ran to my gate to a closed door. One thousand % my fault. But I guess the boarding door was still open. The red coat agent asked me by name, then reopened the door, and removed the non-rev in my seat to let me fly. The FAs were clearly unhappy with the delay but did they give me an unforgettable customer experience that day. A couple of months later, the United-Dao incident happened which made me even more grateful for her/Delta's commitment to their customers.
Yep, Delta has failed me on a few occasions in the past. But every time, they've taken care of me. They will continue to get my business; AS gave me 75k match for my DL Plat but the grass looks pretty yellow from my seat on Delta's side.