高主教vs St. Margaret co-edu

Chess

Just focus on which one is better or the boy.
If you find it difficult to choose between the two, that means they appear almost equally good to you.  Then if I were you, I would choose the one more convenient in location.
For your daughter's path, just desregard it.  There is no guarantee that she will be accepted SMC.  Moreover, what if she is accepted DGS? You never know.