It is more convenient to fly into SNA, but LAX is fine also. We live about 15 minutes away from Disneyland, but we pretty much always fly in/out of LAX because flights are cheaper. Traffic between LAX and Orange County can be awful. If you time it right, it will only be a 40 minute drive, but it can easily become double that time. If you can find a flight into SNA that isn't that much more expensive than LAX, I would do that, just so that you don't have to worry about transportation from LAX and the possibility of it taking 90 minutes.
If you are staying at Disney I'm pretty sure they have a shuttle that goes to the airport so check into that!
Most of the hotels in the Disneyland area offer shuttles to/from the airport as well as the parks. SNA is preferred but LAX or Long Beach (Jet Blue) are good too.