I am deciding between Diez down and the KJUS GLOBE DOWN jackets. The sale person I talked to at the local store told me that North Face Diez jacket is quite uncomfortable to wear since it is not breathable. KJUS Globe ( $450 MSRP) on the other hand is quite breathable. Both jackets are 10 denier Pertex Quantum GL on the outside but North Face is 900 fill goose vs 800 fill on KJUS. So is breathability an issue with this North Face jacket?

Alright. From one outdoor professional who was a technical representative for a major Canadian outdoor company to y'all... Down (the only material we didn't utilize, ironically) is fantastically breathable. Contrary to popular belief, breathability has nothing to do with how much air passes through something, but rather moisture transfer, in the form of vapor. But we're not just talking about down here, we're actually MOSTLY talking about the face (and interior) fabric of the jacket. And while the down is breathable, the face fabric may not be. It has to be VERY tightly woven to effectively be "down-proof," keeping the feathers from poking out all over the place, but unlike a waterproof shell, it does not have to have a laminate or coating on it. So relative to your rainshell, your down jacket will be much more vapor permeable (breathability, remember?) But relative to a primaloft puffy, or even a plain wind jacket? Pretty comparable. Next to a fleece, no contest. The fleece is totally porous. To answer this specific question...they'll both be equally breathable. 900 fill down is a marketing feature, you won't notice the difference between the fill power, you'll notice the difference between HOW MUCH DOWN is actually in your jacket. Of course, no one tells you that :)

like someone else said, Down isn't breathable. What down is excellent at is efficiently holding onto heat. In other words, you sit still wearing a 800 or 900 fill jacket in 60 degree weather and be comfortable, and you can wear it in 20 degree weather and still be comfortable. Start exercising in a down coat no matter who makes it and your butt be sweaty. Pull it off and let your next layer keep your core stable until you take a break.

I would disagree vehemently with huh2572670, in that down jackets can be extremely breathable. I love my down jacket for precisely that reason. It's not as breathable as fleece, but far more breathable than a hardshell. Guy at the store doesn't know what he's talking about.

Down isn't breathable, at all.

both of them have the same fabric so they are going to be equally breathable..