Generally the more money, the lighter weight and more longevity. Usually when new things are introduced like electronic shifting and 11 speed, it goes to the top end Dura Ace first and over time works down to Ultegra, 105, etc. So what you see in 2013 105 components, they might have been 2011 or 2012 Ultegra with a different label (perhaps with some other minor changes)