Although it is still a 95% cotton product, the way these are constructed makes all the difference.  The 5% spandex allows the cotton to be spun much thinner, yet retain its shape after repeated wear and washing.  The thinner weave allows the shirt to breathe much easier, soak up less sweat, and dry out much quicker.  These shirts are cut a little longer than normal, which is great for keeping them tucked in.  The collar is narrow, which is a nice touch; I hate bulky collars because they're not only restrictive and uncomfortable, but they also tend to lose their shape ('bacon neck'), but these won't.