Originally Posted by Crane's
Uninsulated leather is as cold as ice. A real leather and shearling coat is warm because of the shearling which is nothing more than unprocessed wool. Basically it's a fur coat with the fur side in. Not a bad choice but not the best one in my opinion.
Goose down is a tricky thing. The down must be premium quality and there needs to be a lot of it to keep you warm. Once it compresses and starts to settle in those little pockets it's insulation value goes way way down. If the shell isn't absolutely waterproof and you get soaked you're a dead man. Same goes if you rip up the shell and the down floats away in the breeze. The flip side is they are a very light coat which is a prime consideration for mountain climbers etc.
Extremely thick wool coats are very warm and if it gets soaked it does not lose it's insulating qualities. Wool is also very durable and tough. Thick wool is still the number one choice of people who live and work outside in cold climates.
I'm one of those people who has tried all three and I'll stick with my heavy wool coats.
While this might not have been my first answer, Crane's post makes a lot of sense, providing a very thoughtful and logical reply, and hence, I find myself in agreement..."I'll stick with my heavy wool coats"!