Down is still the gold standard as far as getting the most in warmth/weight, but they have issues that some of the latest synthetic "down" materials don't like what were discussing and losing insulation IF they get wet.

Since most of us will never be paddling in sub-zero temps where down really shines, IF I was contemplating spending decent down money on a new bag, I'd have to look long and hard at the newest synthetic down's.

All the best of down, waterproof and the insulation doesn't mat and still insulates if the bag's material does get wet. In many cases they weigh withing ounces of a down bag and generally speaking a lot cheaper.