Leather is not one material. The animal it comes from sets its weight, grain, and feel long before a tannery gets involved. A short field guide to the hides you'll meet in a jacket.
Cowhide
Thick and hard-wearing, with a coarser grain. The go-to for rugged and moto styles. Its strength is real; so is its weight and stiffness, which take time and wear to relax.
Sheep and lamb
Fine, tight grain and a soft, light hand. Drapes beautifully and feels supple from the first wear. Naturally less abrasion-resistant than cow, so it rewards everyday wear rather than hard abuse. In full-grain, it keeps its fine surface and ages gracefully. This is what we use.
Goat
Distinctive pebbled grain, light and surprisingly durable for its weight, with a natural sheen. Common in lighter jackets and gloves.
The point of comparison
No hide is best at everything. Cow trades softness for toughness; sheep trades toughness for softness and weight. We picked the hide that makes a jacket you want to keep on — and then held it to the highest grade so it lasts.