difference between puff and the sweater?
JOSEPH V Insulation type is the only difference. The nano puff is better suited for possible wet environments because the synthetic insulation used will keep its properties when it gets wet. Down on the other hand will become useless if it gets wet, but if it is dry it will be slightly warmer.
MICHAEL C Sweater is down Puff is Not
ADAM E If you mean the Nano Puff, I am not familiar with that style. It does not seem much different than the Down Sweater possibly lighter weight. If that is the case than it would be very light as the Down Sweater is already light weight. I DO know the difference between the Ultralight Down Jacket and the Down Sweater though. I purchased an Ultralight Jacket from another store and had to return it because it was not true to fit (small for a size L) too lightweight and did not seem as durable as the Down Sweater. I can't say enough good things about the Down Sweater. You can always call Patagonia direct and ask someone there.
ALLEGRA N I believe it is the amount of down filling actually. The sweater is a bit thinner thus the fact it's not called a "puff." I work outside in 30 degree weather for several hours a day and it is perfectly warm for me!
ANITA L The nano puff is a totally different material, not down, not as warm, but is lighter, great for daily use. I think it is polyester. The down sweater has much better insulation, most fitted for cold weather. But with Patagonia, even the down sweater is very light and compact. I have both the nano puff and the down sweater to alternate between cold and 'not as cold' weather.