I will add that I own and use bags by Western Mountaineering, Integral Designs, Feathered Friends and, best of all, Valandre. I also had an original, US-made Marmot Mtn. bag for many years.
My choice for hunting and a few other uses, is the Integral Designs North Twin/Andromeda Overbag combo, depicted on their website in the "special" section. This is the best synthetic bag(s) I have ever used or seen in 45 years of active backpack camping.
I prefer good down bags for most uses and Valandre of France currently makes the finest I have seen, with ID, WM and maybe FF right up there. ID makes their bags in a long/broad size that would be perfect for a really big guy and I prefer their "broad" bags for my hunting uses...am into my fourth year with mine and am totally happy with them.
I have used a whack of Kifaru gear, but, not their sleeping bags, so, cannot say anything about them. I would say, tho', that many synthetic bags often are not as "warm" as the makers suggest and I would opt for a warmer bag if my uses went to -0 temps.
Down bags work just fine in damp climates as I have found in B.C., but, require more care and cost more, however, they tend to last longer, so...............