I'm searching for a new pair of puffy pants myself. I would definitely recommend getting a down puffy instead of the synthetic. It makes a big difference in terms of weight, warmth, and packability. Here's the options that I've considered.
The montbell ones are nice, but not having a zipper is a big dealbreaker.
You can order a custom pair from GFG. The only concern I have is I'm not sure about their down waterproof treatment. I think the "DWR coating" is only on the exterior fabric.
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The Kuiu or Stone Glacier ones are probably the best in terms of off-the-shelf IMO. The Stone Glacier has A LOT more down fill, so I'd go with that one. SG also uses probably the 2nd best waterproof-treated down on the market IMO in the AlliedFeather HyderDry.
Like it’s partner jacket, the Grumman Goose Down Pant was strategically designed to reduce weight and maximize packability for backcountry hunts. We have found down pants to be a game-changing piece of gear in adverse conditions. However, many of the products we have used did not pack well or...
www.stoneglacier.com
The Super Down LT Puffer Pants in Vias Camo combines Quixdown insulation with an all-new durable and matte face fabric.
www.kuiu.com
The only reason why I wouldn't go with the Stone Glacier is if you can possibly hold off until AlliedFeather's newer waterproof treated down makes it into the down puffy pants market. It is called
ExpedDry, and it is a PFC-free down with gold particles bonded to the down. I think it will be the
gold standard in down treatment going forward. The only company I've found that is currently using ExpedDry is Katabatic in their men's Tincup jacket, which I have, and it is awesome.... but I'm hopeful that since Stone Glacier is already using AlliedFeather's HyperDry down, they will be the first ones to incorporate it into their pants... even further cementing the Grumman as the go-to down pants in my book.
Sorry for the novel. Wanted to give some background as to why I'd choose the Grumman for now.