The Prana pants have Spandex, which means they have some stretch to them. I don't usually associate stretch with Cordura.
If your pants don't have to be rugged, and you want them to be very light, check out Argon fabrics carried by Dutchwaregear.com. The last I checked, they had 3 weights available. Argon is supposed to be very similar to Pertex. http://dutchwaregear.com/argon-67.html
I'm considering making a tank top and shorts from this to use as camp/town/sleep clothes. Long pants would be next, then a filled tunic/underquilt for my hammock.