I have both the Patagonia Down Sweater and Nano Puff. I find the sweater a fair bit warmer. I think Patagonia's Ultralight Down Sweater is more comparable in warmth to the Nano. The Nano Puff is something I use in spring/fall and mild winter days. I use the down sweater on colder winter days. Backpacking, I take either depending on expected lows.

Down vs. Synthetic, I prefer down. Packs smaller, and a comparably warm sweater to the Nano Puff would be the Mountain Hardware Ghost Whisperer which is about 5oz's lighter than the Nano Puff. But here in Montana we're a fair bit dryer than the SE. Even so, I don't find it especially difficult to keep down dry with a bit of care.


“Perfection is Achieved Not When There Is Nothing More to Add, But When There Is Nothing Left to Take Away” Antoine de Saint-Exupery