Where are you going in Texas? If it's San Antonio or surrounding close by areas, AT&T and Verizon of course work good. However if you're out in the country areas and need unlimited data, Sprint does good. If you live in the major city, Sprint doesn't penetrate buildings well so you'll have horrible data speeds and potentially dropped calls. T-Mobile however, they generally work great in big cities. So if you're not traveling all about in the country areas, you'll get great data speeds and good reception with them.
Overall, this question doesn't have a simple answer.
Ask yourself:
Do I need unlimited data more or do I need guaranteed coverage?
Who offers the best signal in the areas I intend to go?
Do I have a budget and what carriers fit into this?
There are many questions you'll need to ponder on. I'd suggest doing some research and going with the one you feel is the best fit!
Good luck.
P.S I've got T-Mobile and an AT&T Go Phone.