LOL at all of us AAdvantage elites that like to revere Delta like they're Qatar or Emirates. Now, they're doing about 100 things right that American is not doing, but at the end of the day the onboard product between the Big 3 is barely distinguishable beyond uniforms and aesthetics.
The Delta halo effect is real though - they at least kind of believe themselves when they throw around the word "premium" and it starts with the ground experience. The D1 lounges are truly remarkable for a US airline and the Sky Clubs are generally a lot nicer than most of the AA or UA offerings.