I understand that a TrueCrypt volume may be encrypted with a password AND a keyfile.    

As far as I can tell, A LUKS volume may use EITHER a password OR a keyfile, but not both simultaneously for the same user.

 - Can anyone confirm whether this is correct? 
 - Can anyone offer an opinion on whether using a password-protected keyfile is better/worse/equivalent than the combination of a password and a keyfile?