As a teacher & a Catholic, I would say the smaller class sizes would swing it for me BUT what secondary schools do the two schools feed into???
I would love DS to go to our local "good" Primary school in the next road, but the local secondary that most children move on to is not so great. The Boys Catholic Secondary school however, is excellent but the admission criteria after attending Mass and older siblings is that they attend one of local Catholic Primaries. So it looks likely that DS will be going to the oversubscribed Catholic Primary school which is also a 20 min drive away.