Or primal, which is the one that is always going on about nature and primal spirits.Except the "spiritual" part of Spiritual Guardians implies Divine magic
None of the magic power sources really have much real unique flavor of their own. Never have, really.
Arcane is 'Do anything except healing unless you're a bard or celestial sorcerer/warlock'.
Divine is 'Do anything but mostly protection and healing unless you serve a war or fire or magic ore any domain but healing god'.
Primal is 'Do anything that can be vaguely considered natural, so... anything.'.