@Sergio: Ubuntu does not recommend using closed source drivers, so fglrx should never be the default option, or something that is used to provide 3D desktop when the open source driver would also work.
That said, fglrx also has very poor reputation regarding stability, functionality (eg. compiz) or being able to support suspend/hibernation. Since it's closed source, it cannot be fixed either.
@Sergio: Ubuntu does not recommend using closed source drivers, so fglrx should never be the default option, or something that is used to provide 3D desktop when the open source driver would also work. hibernation. Since it's closed source, it cannot be fixed either.
That said, fglrx also has very poor reputation regarding stability, functionality (eg. compiz) or being able to support suspend/