I advise using a site-wide application default file.
Many users create an application-specific defaults file of their own.
Those who do usually read the site-wide application defaults file in order to see what's going on. Application default files may include other application default files, making it possible to separate color customization from language customization, from functional customization, for example. The X Consortium's mail application, xmh, has an application defaults file aptly named Xmh. If you remove this file, its fallback resources are used. In that case it pops up a dialog box warning you that the application functionality will probably not work because the application defaults file is missing.