The big disadvantage of synthetic fiber filling compared to down is the higher weight and packing volume for comparable temperature and performance data. However, this austria rcs data is not so important for anyone who does not want to carry in the smallest possible backpack.
Synthetic fiber models are often heavier and have a larger pack size
The advantage over down is that the insulation properties remain almost unchanged even when wet and siliconized synthetic fibers also dry much faster. The filling in most of the sleeping bags in the test is processed in layers. The air trapped between the four layers increases the heat output even more.
Most of the synthetic sleeping bags in the test therefore offered decent performance. However, hardly any other sleeping bag in the test came close to the warmth output of the down sleeping bags, not to mention the weight and pack size.