Originally Posted by MachThreeSlug

Well it depends. Do you want strong units? Then get a dupes for an extra equip slot.

Are you in it for the waifus? Then get a new unit.

Waifus come first of course but then think about what teams you want to create and what would best help you get there
Is Kerria and Saffron fully maxed out on everything? (for myself I also add Anemone and Alpinia) They are two that will remain among the best at what they do. and also for myself I spend the most resources just for a Raid boss setup. that's the only challenge that I just cannot beat (YET) and Queen Kerria gets a full support staff both for regular battle and for raid boss..but thats me so....it comes back to...
Waifus come first but then think about what teams you want to create and what would best help you get there