On consideration, I don't think using or wearing snake skin, crocodile skin or fur is the same as standard leather. Exotic skins and furs are usually used in ornate, decorative ways, they are usually designed to be a bit flashy. Even if you set aside the objection to killing an animal purely for it's skin, wearing an animal skin that is designed to be a bit flashy makes me cringe a bit. I'm thinking specifically of exotic skins used in boots and bags and fur for jackets and coats. Standard leather, whist it can sometimes be polished up to be a little more ornate, it's first quality is it's practicality and durability. For example, apart from trainers I've yet to find a quality pair of shoes that are not made from leather. Synthetic materials don't wear as well and can smell very quickly. Another thing, would synthetic materials (eg vinyl) be biodegradable?