How does the DAS parka compare to the Arc'teryx Dually belay parka in terms of warmth? The DAS parka is 2oz heavier but it says that it has 170g (6oz) of Primaloft vs the Dually parka saying that it only has 2.7oz of Thermatek (per Arcteryx's website). From this i'd assume the DAS is warmer? I'm looking for a systhetic jacket to complement my Feathered Friends Volant in terms of warmth so was curious if anyone had any insight.

I've owned both of these, one military, the other I bought. Something of note: The face fabric on the dually is much more wind resistant. Now you're thinking "wait, the DAS is too". You're right, sort of. The DAS can get drafty at the seams because the material is sewn all the way through. Its also noticeably larger circumference in the waist, to accommodate those of us wearing guns around everywhere. The dually is longer- not so long that you can sit on the tail to keep your butt dry, but long enough that in the crouched cooking position, you don't expose any portion of your spine or lower back. A welcome feature. When doing your test between the two, be sure to wear them outside and test the hoods. The hood is where a parka will save your life. Buy the one with the hood that you will actually wear. I greatly liked the Dually because the hood was so good at staying dry, and I found it to be easier to precisely adjust than my DAS.

Some clarification on Therma-Tek, the insulation Arc'teryx uses on the Dually. Arc'teryx treats Primaloft with a DWR to create Therma-Tek. This gives it even better wet weather performance; it literally won't absorb water. So when Primaloft loses 20% of it's insulation value when wet, Therma-tek won't. Add to that a super tight face fabric, with no external stitches, that also is DWR treated, and you've got the most weather resistant belay jacket made. One other consideration on warmth. Arc'teryx laminates the insulation directly to the shell (one layer on the liner, one on the face-hence the Dually name), so the loft isn't compressed by stitching that baffling requires.This also adds durability by not having thousands of exposed stitches getting nicked. There are 2 layers of the 2.7 Therma-Tek, so it's going to be quite a bit warmer than the DAS.

The two jackets are definitely similar, and you're correct the DAS should be slightly the warmer of the two. Primaloft is the best synthetic insulation on the market. Save a couple hundred bucks and go w/ the DAS and I'm sure you'll be stoked.