Q. What is the main advantage of creating soft / hard links to a file instead of copies of the file?
A. To make links between files you use ln command. To copy a file you use cp command. The main advantage is access permission. If you want to change the permissions for a a file called foo, you only have to do it on the original. With copies you have to find all of the copies and change permission on each of the copies.
Other advantages :
[a] Create a shortcut for example /webroot/home/httpd can be soft linked at /home/httpd
[b] Ease of management
[c] Save disk space etc
Please note that the link will show permissions of lrwxrwxrwx but that is for the link itself and not the access to the file.