I live in Atlanta and have been with both for many years. when they were aligned I would up on CO to hawaii 90% of the time even if I used delta miles...CO has much better flights going west...DL is better to the islands as CO makes you fly to newark, houston, or even Minneapolis to get there...I hate flying north to go south....right before the split I used my last DL miles to get a great CO flight to cancun...they even beat DL to there. With the new award teir system all the cheap flights are 2 connections, red eyes, or unavailable...what a favor they did us when they spun the new system as being better for the consumer....LMAO
Delta also has pityful customer service...after waiting in line for 30 minutes at the broken kiosks and another 30 to get to the counter we were 3 minutes late checking bags in Vegas....nothing they could do for us but charge us more money...I told them then they were too greedy and they can go bankrupt for all i care....using the last of my wifes skymiles end of the month for MBJ after that DL can kiss it....I now have over 100k in CO and can get another 50 through chase, and 45-60 on UA with offers...looks like star alliance is my new best friend....ATL-HNL or OGG are some of our favorite awards and availabilty is awesome on CO.