I live in the small market US Southeast where Delta has about 60% of the passenger count from Podunk field. Price tends to be pretty much a wash if I can book 21+ days out. (American tends to come up cheapest for close-in cash booking)

Planes- most of Delta's flights out of Podunk are Mad Dogs or 717s. I can tolerate a United Express or American Embraer 135 for significant cost savings, but would rather not if there was no financial incentive for it.

IRROPS- Delta will escalate it a few customer service levels to find me a flight on a partner airline through an unplanned country during ATL ground stop recovery. United has problems rebooking me onto a functional IAH-DEN rebooking with tons of open seats

I've come to learn to stop worrying and love the ATL. And DTW is very, very nice too. I do not get the love for Charlotte some people have. For me, the E gate area there has all the charm of the Paris Metro system. IAH isn't awful, but I just like ATL better.