I (and many of us on these forums) have been using 0.8-0.9oz downproof bags for many years, without any real durability issues. In fact, my Quantum windshirt is one of the toughest pieces of gear I've used...it has survuved many insults that I thought would shred it. So I personally wouldn't choose Epic on that alone. As for the water resistance, well yes, there is a big difference, and if you are not carrying a bivy and sleep in a tarp, then this may affect your decision on which fabric to go with. However, as you aslo oberved, zipperless quilts (could also be called a zipperless, hoodless mummy) are also prone to drafts, making a bivy often handy. So if carrying a bivy, the Epic becomes less useful. You kinda have to decide upfront if you are gonna be a bivy/quilt carrier or not. Adding a zipper and Epic to your quilt (ie carrying an Epic mummy bag, may end up weighing more than carrying some of the more cutting edge bivy bags (cuben/Epic?), but certainly less than carrying a standard silnylon style bivy. Both options work well, but I am not fond of packing away a damp sleeping bag...if I use a bivy bag I can pack that away separately in an outside pocket and dry it through the day, so it's my preference.
Zack: POD 30 baffles are 2" high, centre of baffle height is 4+ inches, the whole thing averaging ~3" when I'm actually inside the bag and pushing the baffles outward. So actual baffle height is less than an Alpinist, but down density is higher. In previous posts I know that someone (Richard N??) has said that down density is a better predictor of warmth than baffle height or total down fill, and that pretty much all commercial bags are underfilled in terms of optimum down density. So although Nunatak uses the 2.5" baffle height as a measure or predicted warmth, this is most likely a red herring as the density is less than other bags with smaller baffle heights. I'm learning that, without a proper thermal test dummy, it is difficult to predict the warmth of a sleeping bag based on baffle height or even loft alone. Along those lines, I have a Hungarian down duvet that has a mere 1" box baffle (same as the POD 30), yet lofts to over 6" in the rest of the boxes. It is by far the warmest thing on this planet in spite of it's piddly baffle height. Combo of high quality down, high density of down, and box design to keep the down in place is what makes it so warm. I notice the Highlite also has some sewn thru baffles, but in a box design, and yet it is still very warm for it's weight...from a MYOG point of view I have been trying for several years to figure out how to make a box baffled bag/quilt (not sewn thru). Does anyone know how???