If you fly CO and book on continental.com, you'll earn 100% EQMs on all Y fares. Considering the sheer number of nonstops ex-IAH, I'd consider that route. But you won't earn full miles on cheap DL tix-- might be important, as it's far easier to mileage run on DL than CO, especially out of texas.

If you never mileage run, I'd say fly CO and use onepass. Some people say reward availability is low, but I'd say it's about the same as my other oft-used FF programs.