I flew mostly CO when I was a NW Plat. Out of AUS I had more flight options, plus the 500 mile minimum gave a nice earning boost on each trip. I miss the service onboard and on the ground, which I found superior to NW and DL. And CO handled my IROPs very well, even as a NW Plat. I got a status match to CO Plat about a year ago but never followed through and it's about to expire. So I'm stuck in the DL (and now AA) worlds.

I haven't been on a CO flight in a year. I hear upgrades are much tighter and the UA merger has made everything uncertain. So I am OK with my "jump" to DL.

You'll probably spend more time in F on DL, at least when there is first class cabin available. Looking at some of your destinations, you may find yourself on a DL 50 seat CRJ more than you'd like. Hard to believe, but they are worse than CO's RJs.