I'll take as objective a look as I can at this, from the perspective of what it would take to win my money.
So the three things here are (a) employee count, (b) meal service on international Y fares, (c) typical fleet seat width and pitch. And of those the first (employee count) isn't even really a direct point of comparison to care about.
So that leaves international Y meals, and seat width and pitch typically found on DL fleet compared to AA. And of those two, I can't say if the DL meal service is better than AA's already and would be moving forward, or if it's behind and is catching up, or whether it's all about the same no matter what. So the one tangible advantage here is the inch extra seat width and pitch.
Small advantage? Sure. But is it going to pull me away from so many direct flights out of my home airport of CLT? It wouldn't. The overall experience on DL would have to be leaps and bounds better and/or for a fraction of the price.
If I was living in and flying out of Charleston, I'm sure it'd be a completely different analysis.
As things stand though the only opportunity Delta has to win my business is on long flights where I have to make a connection anyway. Even then I'm inclined to stick with American to consolidate reward miles as much as possible, so the DL experience would really have to be significantly better overall.