Should be fine, unless you have like violent body outburst while you sleep, and have a history of ripping bags made from heavier duty fabrics. ;)
This fabric is more durable than you'd think. Sure, it's not strong relative to heavy weight nylons, but the seams aren't going to just rip through unless you're trying to destroy it.
As to the difference between the 0.9oz Intrepid and Momentum, lets just say that any difference is indiscernible to the naked eye, or the scale. Pick whichever is most convenient and comes in the color you want.