And many newer down bags compare favorable to synthetics when it comes to performance. New water resistance treatments help alleviate the wet insulation problem. As for weight and size, compare this down bag and this synthetic bag. The down is still lighter and compresses smaller.

Just out of curiosity, why use a compression sack on the tent body? The tent poles don't compress and for every tent I've owned, the poles make for a larger package than the tent itself. I wrap my tent around the poles which makes for a much smaller package than what I see with your stuff sack.