Until my most recent pack, used either 8 oz. Cordura (before I went to BPL), or the 4 oz. PU coated nylon Oxford. Most recent pack is 4 oz. PU coated Spectra Gridstop from Seattle Fabrics when they carried it in dark green, and is very similar to some of the stuff currently selling as Dynema Oxford.
The gridstop is much more durable than any nylon Oxford I've ever used. It also turned out to be more water resistant, not requiring a pack cover after seam sealing with Seamgrip. The only drawback is that after a couple years, the fabric became a little stiffer than it was originally, but this has not caused any problem. I do have some fear that if the fabric continues to stiffen, it will eventually start cracking - but nothing like that has yet occurred.