"Enhanced" government issue generally means "not government issue." They might meet a mil-spec, but if they're poly-cotton, they're not the same as the ones issued to the troops. It's a fairly moot point if they're good quality, but I can't imagine that poly-cotton would be as strong and as breathable as cotton-nylon.

While cotton is sometimes considered a "big no-no," it's not really. In hot weather it's not going to contribute to hypothermia. However, having hiked in Japan and Korea over the last few years, cotton just doesn't dry out well in humid climates and can present a "funk" problem if you're overnighting in the field. Nylon still soaks through in a humid climate, but it dries out well. Cotton gets pretty nasty, particularly socks and undies after a few days in the field in a hot, humid climate. Give me synthetics any day. Cotton is great in warm or hot weather in a dry climate like the American SW.

The military still uses cotton content for their "all climate," general issue uniforms. I speculate that part of it is that synthetics alone are a bit noisy; the cotton blend quiets it down some. The cotton does present something of a hypothermia risk, particularly since the majority of hypothermia cases occur between 30F and 50F, a temperature range in which the military generally wouldn't issue specialized uniforms. On a more positive note, they finally started issuing wicking T shirts and long johns which are a huge improvement over the cotton stuff they issued back in my day. Even though cotton has its problems, the cotton-nylon BDU material is a HUGE improvement over the old OG 507 poly-cotton fatigues which tore easily, didn't breathe well at all, and really weren't all that practical in terms of pockets, freedom of movement, etc. We still had a few of the old OG 107 100% cotton uniforms around when I first got in which were a lot better than the OG 507's, but still the BDU's are a huge upgrade over even the OG 107's, not to mention the fact that BDU's are camo and the 107's/507's were solid OG. I remember being skeptical when the BDU's first came out, but a couple of low-light condition ops more than convinced me. Camo really works, particularly in low light when your eyes aren't able to see as clearly.