4wd vs. quattro

[treilley_at_BANKMARK@conseco.com (treilley)]

     I have a question for you early quattro owners(or any one who can 
     answer it).  My 79 subaru 4wd and my Montero 4wd both had a transfer 
     case that bassically allowed you to lock the driveshafts together when 
     engaged.  How is this different from the early quattros that have the 
     center locking diff?  I mean I understand that an unlocked diff 
     transfers some power as opposed to a disengaged transfer case but how 
     much?  When the center diff is locked, is this the same as a 4wd with 
     the transfer case engaged?
     
     Tim NJ 90CQ, 77Spitfire