Down wins on warmth-to-weight and packed size, and it lasts longer. Synthetic wins on price and keeps you warm when it gets wet. Go down for weight-conscious trips in dry conditions, and synthetic for wet climates and tighter budgets.
| Down | Synthetic | |
|---|---|---|
| Avg. GearScore | 69✓ | 62 |
| Avg. warmth-to-weight | 4.9 /100g✓ | 2.5 /100g |
| Avg. weight | 32.2 oz✓ | 57.1 oz |
| Avg. price | $495 | $174✓ |
The split comes down to what the insulation is made of. Down, the clusters of goose or duck plumage, lofts more warmth per gram than anything synthetic, so a down bag hits a given temperature rating at lower weight and packs far smaller. That’s why down dominates our catalog and every ultralight and cold-weather ranking. Synthetic uses polyester fibers that trap less air per gram, so a synthetic bag of the same warmth weighs and packs more. What you get back is a much lower price and, just as important, warmth that survives when the bag gets damp.
The numbers bear it out. Down bags run lighter on average and reach the best warmth-to-weight figures here, while synthetic bags come in markedly cheaper per bag. The trade you’re really buying is weight and packability against cost and wet-weather reliability. Down also holds its loft for many more years if you care for it, so its cost per season is closer than the sticker price suggests. If your priorities differ, the fill filter and the GearScore algorithm on the full bag comparison let you re-rank around weight, warmth, or value.
How to choose: if you count grams, camp mostly in dry or manageable conditions, and can keep the bag from soaking, buy down. It’s warmer for the weight, packs smaller, and lasts longer. If you camp in persistent wet, like canoe trips or coastal and rainforest hikes, or you want the lowest price, or you need a bag that shrugs off condensation and the occasional soak, buy synthetic. Modern hydrophobic-down treatments narrow the wet-weather gap without closing it, so for guaranteed warmth when wet, synthetic still wins.
Down, clearly. Its clusters loft more air per gram than synthetic fibers, so a down bag reaches the same temperature rating at lower weight and smaller packed size. That warmth-to-weight advantage is why down leads our ultralight and winter rankings. Synthetic closes the gap only on price and wet-weather performance.
Synthetic. It keeps most of its insulating loft when damp and dries faster, while untreated down collapses and loses warmth when soaked. Hydrophobic-down treatments help down resist moisture and dry quicker, but for trips where staying dry is impossible, like paddling or persistent rain, synthetic is the safer choice.
If weight and packed size matter to you, usually yes. Down costs more up front but is warmer for the weight, packs smaller, and holds its loft for many more years when stored uncompressed and kept dry, so its cost per season is closer to synthetic than the sticker price implies. For budget buyers or wet climates, synthetic is the smarter spend.
Down, generally. High-quality down retains its loft for a decade or more with proper care, whereas synthetic insulation slowly loses loft, and therefore warmth, as it’s compressed over the years. Store either one uncompressed to extend its life. The effect is just more pronounced with synthetic.