I've lived in both cities and indulged in the carnal delights offered in each. I can honestly say that, in my humble opinion, the Providers in Dallas are MUCH better! That means in terms of looks, quantity and variety (more open-minded, more choices such as individual providers and AMPS).
On the other hand, Houston has Dallas beat hands down when it comes to topless/gentlemen clubs. There are more clubs and they have more variety. Granted, Houston is much larger than Dallas, but even if you were to take the top 10 clubs in each city Houston would still beat Dallas. The dancers in the Houston clubs are more erotic, suggestive, bountiful and talented when it comes to dancing and available extras.