It seems in the past 20 years there has been an evolution from the old BDU to what are called battle pants. There is much discussion on the attributes of various brands such as Crye Precision which seem to be focused on appearance (camouflage), functionality, durability and neat features such as internal knee pads.
As a traditional bowhunter and former mountaineer, what seems absent is information on how quickly the fabric dries and how it contributes to body heat loss. I am struggling for the correct term but on one end there is cotton which gets wet easily, like a sponge, is slow to dry, and greatly steals heat from the body. Cotton also does not allow minimal passage of moisture among layers of clothing and has a negative insulation value. Wool is at the opposite end. Also, how noisy are the fabrics used in combat pants. Cotton and GoreTex are loud when rubbed up against sagebrush but most wool weaves are pretty quiet.