Well, after spending a bunch of time looking at potential upcoming flights, I went with United MileagePlus over AC because there's a good chance I'll be doing the Houston/OKC/Denver triangle more than once.
Already have 4 United flight segments under my belt, and because of a mechanical-caused delay, they are going to owe me a flight credit or points credit too.
I really hope I don't end up flying enough to get status, but hey, seems silly not to at least sign up.
On a side note, the united app is really helpful when you need to rebook or change flights due to a delay.