In addition a portable CMM can probe a wider range of things, generally. Due to its flexibility occasionally you may run into something where you have to fixture it in order to keep it still while you probe it, but fixturing may be impossible or not an option. You would think this would be a problem with a fixed CMM as well, but if you can take a part to the CMM this shouldnt come up in the first place. The ability to be able to go anywhere and probe something with it is very useful.