Even when you turn off media syncing, BlackBerry Link might backup your device's on-device storage. So far all BlackBerry 10 devices ship on-device storage marketed at 16GB. Both this and the standard BlackBerry 10 backup process currently takes longer than BlackBerry Desktop and BlackBerry OS 5/6/7.
Originally Posted by BriniaSona
BlackBerry will definitely address this in the future just as they made backup speed improvements in BlackBerry 6 and 7.x as well as in BlackBerry Desktop 6.x and 7.x that made backups using those products much faster.