USB is not as fast as LAN connections. USB is usually always a bottle neck. Also having a large drive size, the more files you put on the drive, the longer it will take the router to scan and catalog the files each time you add files and reboot the router to scan the drive. If your doing small xfers then performance is negligible. If your doing lots of large data xfers, and want good performance, network LAN is the way to go. Not trying to discourage, just be aware of this and alternatives.
Good Luck.