Based on KUIU's objectives (mountain gear, light weight, etc) one would reasonably expect to see bags cut/sewn a little slimmer... smaller... snugger. Less internal space means less air volume to heat, and that means increased efficiency along with a better temp rating for a given size/weight/fill. Bigger bags are more comfortable but come at additional weight and reduced efficiency. I knew that when I bought my Sequoia which is more than enough space for my 6-0 / 200 lb body. I also knew I wouldn't be backpacking it for sheep or goats. I also own a WM TerraLite which is a far lighter (weight) bag and rated 15-20 degrees warmer than my Sequoia. Both bags hit their temp rating squarely on the head for me. The TerraLite is a great bag for (example) caribou or spring bear hunts where temps will seldom drop below 25F.
I have owned a good many down garments from Feathered Friends and they are 100% excellent in design and quality. I would absolutely recommend their sleeping bags based on reputation. Maybe I'll buy one some day. If their bags are as good as their garments then I'd rate them just as good as Western Mountaineering.
Count me as one of those NOT down on KUIU bags. For almost equal money I will spend mine on a sleeping bag made by an acknowledged top-end company specializing in their manufacture and having multiple decades of experience to draw on. For reference: I was around back when Jan Sport, Marmot Mountain and North Face were high-end boutique builders of backpacking and mountaineering gear. My first good bag was an original NF Ibex built in California and I had it 35 years before selling it (and another) for more than I paid new. Those companies (and KUIU) make good stuff today but they're definitely at least a notch or 2 down from premier companies like WM, FF and very few others.
Excellent commentary, as usual, and I would only add that the current "top" bags, IMO, are mostly differentiated by certain minor features of design. I have found some details I prefer on each of WM, FF, Valandre and the orginal Integral Designs bags made in Calgary, Canada as well as my old, original Marmot Mtn. Works bag made in Grand Junction, CO, one of the earlier, hot cut ones.
Right NOW, I tend to prefer the WM bags due to that superb stiffener behind the zipper, a brilliant feature, IMO and the wider models offered as standard, more so than FF or especially Valandre. I asked Niels of V. for a "wide" model, std length "Bloody Mary" as I had suggested a bag of this level of "warmth" and called it the "Riotous Red", but, no luck......
Sooo, for now, WM is top of my list, all issues considered. That said, go on PHD's site as they offer some interesting models and will build as you choose. They have the "rep" and some of their stuff is VERY attractive.
