Overcoat
While the overcoat may look more professional in some opinions, I like the blazer/suit coat look for medium temps and the leather coat for cold temps. When it's -20 and blowing 30kts out of the north east and your in the mountains there is nothing that stops the bitter cold like a leather jacket!
Plus, I'm not a big fan of the long coats that are fabric/poly style as they tend to be high maintenance to keep nice looking and collect a lot of lint,crumbs, etc.