Assuming Casper is installing your vendor packages without issues then the big advantage is they require no extra preparation for deployment. Drop'em in Casper Admin and go. And they won't have any potential cruft that may be left over from your own repackaging. They're "clean".
My packaging philosophy is not to repackage software unless I have to do so. I manage preferences separately whether I can use MCX or have to push preference files. I also maintain separate license files apart from the application installers and preferences.
This is, more or less, an extension of the modular imaging philosophy. I can swap out any one of these items for another without impacting the others.