Priority boarding, food and beverage service during boarding, nearly guarantee luggage storage, off the plane first.

If you’re flying economy and if you’ve checked your bags then you’re right, there isn’t much difference.

That said, it’s pretty obvious the interior features that Delta purchases versus Southwest are noticeable. In-flight entertainment monitors in the head rests, more space in First class and comfort plus.

As for the delays, I’m pretty sure Southwest ranks towards the bottom in terms of most delays. Not to mention, delays are mostly an issue of weather and volume of flights anyway.