Synthetic isn’t all bad, but it’s not ideal, either. Down jackets provide better insulation, and since it’s a natural filler, it allows for more breathability. Whether it’s air traveling through the lining of your jacket, or ensuring that you don’t overheat, you get a more versatile and natural insulation with down material.
Synthetic material does tend to cost less. When you’re comparing synthetic and down jackets side-by-side, you really have to focus on the fill power. Some synthetic jackets will use different forms of measurement when defining how insulated or powerful their jackets are, which is why it’s very important to keep your eye on customer reviews here.
Synthetic materials also add more weight to your jacket, so if you’re bringing this along for camping, it’s either heavier on you or an extra bit of weight in your pack. Either way, not the best thing to have. Synthetic also has a very difficult time compressing, usually bustling inside of their drawstring bags. This said, synthetic insulation generally performs better when wet and offers a vegan-friendly alternative for those who want it.