Placentia looks like the better choice from the standpoint of schools. I am wondering, why did you skip over Fullerton, which is between the two? Fullerton has some great schools. You can also check API scores on line for most schools. These scores tell you how the school is doing academically, compared to other schools in the state. You might also want to check out sites like greatschools.net. Not only do they have API and other test scores, they also have parent's review.
My advice to you is, find a realtor who really knows the area you are looking in. They will know where it is preferrable to live, based on your criteria. Let me know if I can be of service in any way and Dare to Dream.
Real Estate Consultant
RE/MAX Palos Verdes Realty