|If You mean |
copy dev1:[dir...]filespec dev2:[dir2...]
backup dev1:[dir...]filespec dev2:[dir2...]
there is not much difference, except different behaviours for modification dates and security settings (protection,ACLs).
And copy by backup can exclude alias files from multiple copies (/NOALIAS), and does not copy content of files set NOBACKUP (unless /ignore=nobackup).
But backup of course does much more than copying files:
create backup archives (save-sets) on disk or tape,
disk-image backups either disk-to-disk or disk-to-saveset, preserving volume-structures, and "bootability".
Joseph Huber, http://www.huber-joseph.de