I'm curious as to what most people's views are on this subject. Personally, I will almost always prefer symlinks unless I have no other option -- I find that it is far more obvious when someone is navigating the file system, but, on the other hand aliasing is more platform independent. Windows XP, for example, doesn't have anything remotely comparable to symlinks (NTFS junctions are not interpreted correctly by at least some environments), which means that anything which relies on symlinks in a *nix based system cannot be transferred. (I know that Windows 64x OS's have symlinks, but I've not seen if they can be read correctly by the environments previously mentioned)
In addition to this, I was also wondering which is considered faster. Is this even possible to know? Do you have a conjecture? I would imagine that since symlinks are generally more low-level than Apache it would make sense that they would be referenced faster, but, on the other hand, I would guess that Apache is required to do a lookup in either case so it would be disk read dependent.