And the OP clearly has no idea what he is doing.
look at the fit I provided .
PD gives +14.7% shield passive regen for 22 CPU. DC gives +14.29% shield EHP and regen for 30 CPU, plus some armor and hull EHP.
PD gives more regen, more PG, uses less CPU, gives cap bonus, basically the only way a DC is better is when you need EHP, that is when your shield tank is going to break.
DC is the WORST low slot you can use for shield passive tank.
So don’t use a DC.