Sleeping bags are typically compared based on what factor?

Sleeping bags are often compared based on loft, as this refers to the amount of insulation and the bag's ability to trap heat. Loft is crucial for warmth because it indicates how much air is trapped in the insulation, which is essential for thermal efficiency. A greater loft typically means better insulation and warmer sleeping conditions, making it a key factor in evaluating a sleeping bag’s performance, especially in cold weather scenarios.

While other factors like weight, durability, and fabric type also play important roles in choosing a sleeping bag, they do not directly affect its thermal efficiency in the same way loft does. Weight might be more important for backpackers looking to minimize gear load, and durability and fabric type are vital for durability and comfort, but the primary consideration for warmth and insulation performance lies with loft.