Worth noting that female platinum units of the same class provide less than 1000 xp, making them less efficient uses of spirits than platinum armours. Personally, I tend to find platinum and black spirits to be the choking point for leveling units rather than the platinum armours, so prefer to save them for use with armours or during events that boost xp gain enough to make other units more efficient (though such events always exclude event units from providing boosted xp).