Those 15 Bandar archers can be moved around the map, join other armies or defend provinces. The PD on the other hand can't ever attack, can't ever move and is a total waste of money if you never attack the province.
On similar grounds, surely the cost of Prod-3 for Ulm should be taken into consideration. Some nations need good scales to get the best out of them, and some need a good bless. As I see it, it's all part of the intricate web of race balance.