Ah, makes sense, this would be a preferable method for a user with multiple environments and one user. Or for more general env variables.
Using the xfce built-in method, makes a .desktop file which may provide easier implementation of some things. And would only be launched when user is loading xfce environment (which could probably be modified to work for various environments within the . desktop file if needed/desired). (Following the freedesktop specifications linked below by @cscs)
This is the location where the list of applications that should be automatically run on login is stored. Each autostarted application is represented by a .desktop file (see the Desktop Entry Specification for details).
Interesting knowledge to me.