what are the most important changes in master pages in SharePoint 2013 than SP2010? Here changes means new feature addition?
There are a lot of changes between the v4.master (2010) and the seattle.master (2013)
Maybe the most relevant is the suitebar and the ribbon bars.
All of the features from the 2010 are present in the 2013 version, however some of them could be hidden like the breadcrumb, you can read more about in the link bellow.