I am shopping for a 0 degree bag and am in a dilemma over shell material. On the one hand, there is the Montbell Spiral Down Hugger 0 which is 2 lb, 9 ounces but uses DWR treatment on a 12 denier nylon.
On the other end of the spectrum is something like the Feathered Friends Snowbunting which is made with an eVent shell, at ~2 lb, 14 ounces. (I called them and the rep said the eVent adds about 1.5 oz over the listed Epic fabric)
EVent may seem like overkill at first but then I realized that out of all the water proof fabrics, eVent is the most breathable. (but not more so than a plain DWR) For instance, FF's other fabric is Epic by Nextec, but reading reviews around the internets it seems that eVent is WAY more breathable. To me, this seems more important than any additional water proofness that it offers.
I guess the bottom line is that I anticipate my tent will always have a lot of condensation, so I want to make the smart choice. It is already an expensive purchase so I am not considering the price differences a factor. Also, 5 ounces seems worth it to me if the tech really is useful. In other words, I'm not considering price or weight, only utility of the upgrade here.