My favorite one to backup data is:
ROBOCOPY "C:\folder" "C:\new_folder" /mir
/mir is for mirror. You can also use /mov to move files. It reproduce the exact same folder. It can delete/overwrite files as needed. Works great for me. It's way faster than xcopy / copy. It's built in Windows as well.
Source: http://technet.microsoft.com/en-us/library/cc733145.aspx