oh goodness i guess i need to come in here and moderate. i am what they would call an expert on both sides of this conversation, Delta vs. Southwest.
if you want to have a debate about which is the better airline, there are too many factors to do that sufficiently and no mind is going to be changed.
i fly delta for work, weekly. i can't imagine flying southwest for consistent work travel... i hate the cattle boarding, i hate not knowing where i'm going to be sitting, and i hate that there are no Comfort+ or First Class upgrade opportunities which include more leg room and free booze. Delta's in flight experience is better, there is no debating this. the entertainment options are incredible and every week i'm watching a movie that was just in theaters a couple months before. yesterday's movie was Logan. and it's all free! because i fly delta i will soon have access to the Delta Sky lounge that is in any major airport in the united states, and i will soon be booking flights to Hawaii for my wife and myself next year all paid for with skymiles, with a probable upgrade to first class. Hawaii!
living in kansas city, however, means you are going to be forced to fly southwest once in a while. they have by far the most directs, and yes, they are almost always cheaper in my experience. 11,000 points for a round trip flight to mexico city? that's asinine. by using my CSP i earn enough points that by the time i have to fly for personal reasons, i can pay for it with UR points directly transferred to Southwest. the same cannot be said for Delta. the convenience of free cancellations/changes cannot be overstated. and, no bag fees.
Delta is a better, more robust airline but that doesn't mean it is the airline FOR YOU.
the more you know.