Sleeping bag: down or wadding?

Quechua uses two types of sleeping bag filler: wadding and down.

Wadding is a synthetic filler, 100% polyester. 

It withstands washing well. There are two versions: warm, comfortable wadding that's heavy and not very easily compressed for "comfort" sleeping bags; and a more lightweight, more easily compressed wadding for "compact" bags.

Down is a natural filler.

Often mixed with feathers, it is used in bivouac sleeping bags and compact sleeping bags for sleeping high in the mountains. Duck and goose down is especially compressible and warm. However, it is rarer and thus more expensive than wadding.