Sorry that I can’t add much to your post, but since I have been looking for a belay parka that is warmer than my DAS, I figured I’d give my thoughts.
Not knowing your intended use, I can’t say whether to recommend a superlight shell fabric like Quantum, but keep in mind that FF is now using a Nano fabric from Schoeller that is supposed to be very good…
Also keep in mind that Nunatak will build their Skaha to be a bit warmer and more detailed for winter use: a full zip, elastic cuffs, more down, etc. It is somewhere on their site, but I can’t find it now.
If you are planning on wearing a shell over the parka, it will be easier to just get an Epic or other resistant fabric, as the hardshell will have to be very large not to compress the down in the jackets you are looking at.
About the Patagonia- looks nice, but the inner fabric is the same as my DAS, and I have damaged that pretty badly due to rubbing against my harness and from contact with Velcro- it is not as durable as nylon. Not a big deal in a synthetic, but for down I’d be wary. They also don’t say how much down is in the jacket.
Others to look at are the Montbell Permafrost- baffled with welded seams but 9oz of down is the same as FF Hooded Helios or Volant. Why not a hooded Volant?
Also, check out PHD. If you are willing to get a custom piece by Nunatak, consider their Yukon and Hispar. I seriously wish someone who would buy one of these so I could check them out- the Hispar looks amazing. Crazy expensive given the exchange rate though…
The best bang for the buck, Rab Nuetrino Endurance. Not baffled, but a heck of a price and great weight.
http://www.prolitegear.com/pl_rab_endurancejacket.htm
Edit: check out Ebay for the Pat down parka. I just did, and the pics show the down chambers as being very large- I wonder if that would create any cold spots.