Which filling: down or synthetic fibre?

Insulation:
down provides around the same heat performance as synthetic fibre, which is twice as heavy.

Moisture sensitivity:
down's performance deteriorates significantly if it gets wet. It takes a little longer to dry than synthetic fibre. Down is therefore not really suitable for very damp climates.

Durability:
down retains its loft far longer than synthetic materials. The lifespan is almost twice as long.

Cost:
the price of a down sleeping bag is around double that of a synthetic fibre model with a comparable insulation rating. This is due to the fact that the down version will last almost twice as long.

Sleeping climate:
down is capable of regulating the temperature and moisture in the sleeping area. The resulting pleasantly warm and dry sleeping climate guarantees a restorative night's sleep. However, there are limits to the ability to adjust a down sleeping bag. If the sleeping bag is too warm and causes you to sweat too much, the excess moisture can impair the insulation properties of the sleeping bag.