a friend lost is a friend lost.. no matter how it happens, it is not pleasant..
good friend moving away still can keep in touch in this modern world. Having a good friend lost who lives right close by is worse. Not an easy thing to be seen near and dramatize the situation.
It mostly depends on how close the friend is. A good friend who lives close and loses touch can be harder, since the pain of trying or wanting to see her can be very hard to deal with. The good friend who moves far away can still be contacted, loved and vice versa.