Well, I'd venture that the Dallas County season ticket holders probably have them in multiples bigger than the Bexar County folks. Tarrant isn't as burnt orange as you'd think. Too many OU/TCU/A&M people.
If you're implying that Houston is somehow "winning" the season ticket holder battle, consider that Harris County has twice as many people as Dallas County (and the disparity seems to be growing), and Houston is a closer ride.
Including the surrounding counties, Houston is at about 2300 and DFW is about 1800, considering the population difference, the ratio is about right.
Plus in Dallas you have many more schools alumni than Houston, OU, OSU, Arkansas, Tech, TCU, SMU, Nebraska, Kansas, KState, UNT, ATM, Houston has ATM, Houston, Rice, LSU and some of the above mentioned but not in the same numbers. The statistics are about right.