If there are job openings in IAH, definitely take the offer. IAH is always busy, and I know a lot of people that transferred from my hub to Houston. You will get hours there. Many people love it because of the QOL; and the cost of living down there. Just as long as you can take the heat, you are great. If I didn't have a lot of ties up here, I would have transferred down there 15 or so years ago.
ORD is still the "Mother Hub" in the UA system, but IAH (old CO) is a pretty good place to work in. Kirby has be trying to improve the UA network and I think the oil business is trying to stabilize somewhat. So IAH will be near or at 600 flight operation. Plus we still have offices in IAH (my pay still gets processed there)