Since it hit the market I have told you that I am on the fence as far as treated or water resistant down goes and until the issue is settled that will remain the case. My advice, when choosing between down and synthetic insulation layers, is simple. If the temperature warrants (stays below freezing) and you are certain that you can keep it dry then use down otherwise go with a good synthetic. My favorite synthetics are Primaloft, Climashield and Lamilite. Much of my favorite goose down comes from Western Mountaineering and Feathered Friends although I have pieces from Patagonia, The North Face and Canada Goose that are outstanding too. Regardless of which insulation you pick make sure you use it in a system that includes proper base and shell layers.
Kuiu recently put out a Youtube video “to try to make it clear which product (Super Down or the new Kenai synthetic) is the best choice for each different situation”. In the video, Kuiu founder Jason hairston, says that he uses the Super Down jacket when: he is really worried about weight, he is tight on space and needs the compressibility of down like on a backpack hunt, it probably isn’t as cold when he is hiking or climbing, he doesn’t need to be in insulation and when breathability is not an issue because the Super Down jacket is coated which makes it less breathable. He says that because the Super Down jacket is coated it is less breathable therefore warmer.
He refers to the 3DeFX in the Kenai as active insulation and chooses it when it is cold but he is going to be climbing and needs the maximum breathability of an uncoated fabric. He adds that it is not going to be as warm as down but it is something you can wear when you are climbing. He concludes by saying that he hopes this helps. I am not sure that it does.
I have not had an issue with the breathability of my insulation pieces primarily because I am not wearing them when breathability is an important issue. I also don’t want to be wearing anything puffy when I am wearing a pack because the weight compresses it down to nothing which renders the part that covers my back useless. Also, this whole discussion seems to ignore the use and purpose of the shell layer.
I guess this all boils down to one question. Do you trust your treated down? If the answer is no, please refer back to my advice in the first paragraph. It has proven to be sound for a very long time.