Fly into whatever offers a significantly cheaper fare. There have been times when the fare difference was $200 per person round trip by picking a particular airport. That's not chump change. We're talking about $800 for a family of 4. So check the fares at all the LA area airports. Sometimes, there is a deal at one that there isn't at the others. Other times, there is no difference. And whichever is cheapest is not always the same. Sometimes it's Orange County. Sometimes it's LAX. Sometimes it's one of the others.
If none are significantly cheaper than the others, I would fly into Orange County.