Of those two choices, I woold prefer Dallas/Fort Worth over Houston.
Both of them are large cities with a lot of choices for nightlife and for restaurants.
I think Houston is just too big, too sprawling, too congested and too commercial. Dallas is a bit more manageable.
If I had my choice of any city in Texas, I would probably choose San Antonio or Austin. Both of those cities are smaller than either Houston or Dallas, but they are more interesting. San Antonio, with its Riverwalk, and its flourishing Hispanic culture is one of the most beautiful and interesting cities in Texas. It has a variety of nightlife, a nice selection of restaurants and a vibrant local music scene particularly famous for Tejano music. Austin is a smaller, quieter city with a nice seclection of nightlife and restaurants and a very active local music scene. It has become known as the Western Nashville, because of its flourishing music business that features not only Country and Western Music but many other varieties.