They're pretty fleshed out for Werewolf, getting probably a good fifth of the core book with lots of time in most of the Werewolf supplements. In Mage, you get 2 or so pages about the spirits in core, which necessarily leaves a pretty basic picture and basically need to look elsewhere to really understand them.
Systemically they're identical, although the Mage core just lays out the barebones of their mechanical capabilities.