Here is what you really need to know:
1) All down is not created equal. Goose down is better than duck down. Down from mature geese that live in cold climates produce larger down clusters that trap more body heat keeping you warmer as well as lofting up to produce a comforter that is puffy without weight. Fill-power is the measurement of a down cluster’s ability to loft up after compression. 650 fill-power and up is considered luxury quality. The higher the fill-power the greater the thermal properties and the puffier the comforter. There is also cluster count to consider. This is the percentage of whole down clusters as opposed to pieces of broken down known as “fly”. Canadian White Goose Down is considered to be the finest in the world. Siberian, Hungarian and Polish white goose downs are premium qualities and the very rare Eiderdown, the ultimate in softness and warmth without weight, is the best down in the world.
2) Down will eventually “leak” out of anything other than a cotton cambric downproof fabric. What makes the long staple Egyptian cotton fabric downproof is not just a high threadcount but callendering. This is a...