Thanks for the response!
It's true that especially in early game, crew quarters is not something you have in abundance.
Personally, though, I think the worst case scenario for having to using crew quarters is much better than that for having to use cargo hold (see below), but I can imagine other players agreeing with you in that cargo hold is preferable.
Worse case (crew quarters):
After taking on freed slaves as passengers, your ship is overpopulated for a short time and you lose morale.
Worst case (cargo hold):
You do not have cargo hold installed in your ship (such was my case), and must do the following to proceed the quest:
Unless you killed all of the pirates and their shipyard, you will not be able to add cargo hold to your ship as enemies are still nearby.
Therefore, you must leave the sector, repair ship (if required), add cargo hold, go back into the sector and look for the freed slaves 'good' floating somewhere in the sector, as there is no visual prompt.