>>2589946synthetic down, per weight, by a long shot.
and by the way, apex is the best synthetic down material on the market. the rest don't match its performance on all metrics. and anything made of recycled plastic will NOT perform the same, maybe 70% as good.
but why does it matter?
fleece is a breathable active layer you wear while hiking, and synthetic down is an insulating layer you wear while standing around at camp or when you stop to make lunch or puff a cig.
you'd never use them for the same purpose. any time you'd pack a synthetic down jacket, you probably also want a fleece with you.
