Symbolic Link vs. Alias

Well a symbolic link is a filesystem function Alias is more of a special kind of file.

-s links are one way street point to a location regardless of what is there or if that changes. If you rename the destnation folder it points to nothing. If rename some other folder to the right name it now points there. A symlink in terminal will be understood just like a hard link.
Uses the icon of the original folder, file ..

Alias is a two way stree it points to the file not its location like a hard link.
You move the file (on the same partition) the alias won't break.
Alias can use its own icon. Alias doesn't work in the command line.

There are also hard links which are effectivly true addresses. The hard link "is" the file, just that there can be multiple hard links from different locations point at the same file. As long as one hardlink lives the file is not deleted.
It is basically a way to break the usual folder structure.

For the Movies, Music .. folders I would just use symbolic links. I never really tried what happens to a hard link if it points to a drive that isn't mounted currently.

 

Hard links can't cross devices. All hard links to a given file must be on the same disk or partition volume.

http://en.wikipedia.org/wiki/Hard_link