I also live in the desert Southwest (USA) and light, loose cotton works well for me. As I understand it, cotton is also a common choice among participants in the Badwater Ultra.
This is a dry environment where moisture evaporates so quickly the performance of the fabric hardly matters. I'd be more interested in what marathon runners in Houston have to say.
Quoted message said:
Consider why natural selection favored a body that sweats in the first place.
Evaporative cooling is superior with synthetic fabrics. The rate of evaporation is what counts.
