export import is logical backup.
it cannot be termed as a full backup.
if you loose data, you can restore it with exported dump.
if you lose your datafile? ?? export cannot help.
with rman you can backup the control file, archive logs and datafiles.
if u create a catalog database for rman, you backup/restore(full and point-in-time)/clone any number of databases.
and with rman you can also backup/restore a particular tablespace. 
with rman, options are really flexible.